Re: [ccp4bb] Comparing two proteins
Hello Rex, most programs probably use similar algorithms for superpositions, so you can pick your choice: - O - lsqman - lsqkab - coot - ... are all similarily comfortable to use in my opinion. Tim On Wed, Apr 13, 2011 at 09:18:27PM +0100, REX PALMER wrote: Dear All What is the best program to use for comparing two protein structures which are very similar both structurally and wrt aa sequence? ie to get the rms deviations both generally and in selected regions. Rex Palmer Birkbeck College -- -- Tim Gruene Institut fuer anorganische Chemie Tammannstr. 4 D-37077 Goettingen phone: +49 (0)551 39 22149 GPG Key ID = A46BEE1A signature.asc Description: Digital signature
Re: [ccp4bb] Comparing two proteins
ESCET is also very useful to reveal small, but significant differences. It also identifies conformationally invariant regions for superposition. http://schneider.group.ifom-ieo-campus.it/escet/index.html Gergely On Thu, Apr 14, 2011 at 9:34 AM, Tim Gruene t...@shelx.uni-ac.gwdg.de wrote: Hello Rex, most programs probably use similar algorithms for superpositions, so you can pick your choice: - O - lsqman - lsqkab - coot - ... are all similarily comfortable to use in my opinion. Tim On Wed, Apr 13, 2011 at 09:18:27PM +0100, REX PALMER wrote: Dear All What is the best program to use for comparing two protein structures which are very similar both structurally and wrt aa sequence? ie to get the rms deviations both generally and in selected regions. Rex Palmer Birkbeck College -- -- Tim Gruene Institut fuer anorganische Chemie Tammannstr. 4 D-37077 Goettingen phone: +49 (0)551 39 22149 GPG Key ID = A46BEE1A -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.10 (GNU/Linux) iD8DBQFNpqOSUxlJ7aRr7hoRAuLIAJ0Tf�㤛聬틢谋擄ਏ� x3TuOjPcJqLZgL1vnANuUV0= =vQE1 -END PGP SIGNATURE- -- Gergely Katona, PhD associate professor, docent Department of Chemistry, University of Gothenburg Box 462, 40530 Göteborg, Sweden Tel: +46-31-786-3959 / M: +46-70-716-7586 / Fax: +46-31-786-3910 Web: http://www.csb.gu.se/katona, Email: gergely.kat...@chem.gu.se
Re: [ccp4bb] Comparing two proteins
Yes, I forgot about escet. The more up to date wab address is http://webapps.embl-hamburg.de/escet/ even though that page still lists Thomas' address in Italy Tim On Thu, Apr 14, 2011 at 10:05:47AM +0200, Gergely Katona wrote: ESCET is also very useful to reveal small, but significant differences. It also identifies conformationally invariant regions for superposition. http://schneider.group.ifom-ieo-campus.it/escet/index.html Gergely On Thu, Apr 14, 2011 at 9:34 AM, Tim Gruene t...@shelx.uni-ac.gwdg.de wrote: Hello Rex, most programs probably use similar algorithms for superpositions, so you can pick your choice: - O - lsqman - lsqkab - coot - ... are all similarily comfortable to use in my opinion. Tim On Wed, Apr 13, 2011 at 09:18:27PM +0100, REX PALMER wrote: Dear All What is the best program to use for comparing two protein structures which are very similar both structurally and wrt aa sequence? ie to get the rms deviations both generally and in selected regions. Rex Palmer Birkbeck College -- -- Tim Gruene Institut fuer anorganische Chemie Tammannstr. 4 D-37077 Goettingen phone: +49 (0)551 39 22149 GPG Key ID = A46BEE1A -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.10 (GNU/Linux) iD8DBQFNpqOSUxlJ7aRr7hoRAuLIAJ0Tf�㤛聬틢谋擄ਏ� x3TuOjPcJqLZgL1vnANuUV0= =vQE1 -END PGP SIGNATURE- -- Gergely Katona, PhD associate professor, docent Department of Chemistry, University of Gothenburg Box 462, 40530 Göteborg, Sweden Tel: +46-31-786-3959 / M: +46-70-716-7586 / Fax: +46-31-786-3910 Web: http://www.csb.gu.se/katona, Email: gergely.kat...@chem.gu.se -- -- Tim Gruene Institut fuer anorganische Chemie Tammannstr. 4 D-37077 Goettingen phone: +49 (0)551 39 22149 GPG Key ID = A46BEE1A signature.asc Description: Digital signature
Re: [ccp4bb] Comparing two proteins
This tool looks cool also (especially to all the maximum likelihood fans of this list I guess): http://www.theseus3d.org/ --- Theseus is a program that simultaneously superimposes multiple macromolecular structures. Instead of using the conventional least-squares criteria, Theseus finds the optimal solution to the superposition problem using the method of maximum likelihood. --- Tim Gruene wrote: Yes, I forgot about escet. The more up to date wab address is http://webapps.embl-hamburg.de/escet/ even though that page still lists Thomas' address in Italy Tim On Thu, Apr 14, 2011 at 10:05:47AM +0200, Gergely Katona wrote: ESCET is also very useful to reveal small, but significant differences. It also identifies conformationally invariant regions for superposition. http://schneider.group.ifom-ieo-campus.it/escet/index.html Gergely On Thu, Apr 14, 2011 at 9:34 AM, Tim Gruene t...@shelx.uni-ac.gwdg.de wrote: Hello Rex, most programs probably use similar algorithms for superpositions, so you can pick your choice: - O - lsqman - lsqkab - coot - ... are all similarily comfortable to use in my opinion. Tim On Wed, Apr 13, 2011 at 09:18:27PM +0100, REX PALMER wrote: Dear All What is the best program to use for comparing two protein structures which are very similar both structurally and wrt aa sequence? ie to get the rms deviations both generally and in selected regions. Rex Palmer Birkbeck College -- -- Tim Gruene Institut fuer anorganische Chemie Tammannstr. 4 D-37077 Goettingen phone: +49 (0)551 39 22149 GPG Key ID = A46BEE1A -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.10 (GNU/Linux) iD8DBQFNpqOSUxlJ7aRr7hoRAuLIAJ0Tf??? x3TuOjPcJqLZgL1vnANuUV0= =vQE1 -END PGP SIGNATURE- -- Gergely Katona, PhD associate professor, docent Department of Chemistry, University of Gothenburg Box 462, 40530 Göteborg, Sweden Tel: +46-31-786-3959 / M: +46-70-716-7586 / Fax: +46-31-786-3910 Web: http://www.csb.gu.se/katona, Email: gergely.kat...@chem.gu.se
Re: [ccp4bb] Reproducing crystals.
Jun Yong and Jobichen (I've mentioned this before, but ) - both of your projects jump out as very good targets for microseeding with random screens. This method often gives extra hits and better crystals because it is more likely that crystals will grow in the metastable zone. It often reduces the *need *for optimization. Read Allan D'Arcy's excellent paper, plus Obmolova et al for a spectacular example. Our web site has some recent tips that may help you too. Good luck Patrick D'Arcy, A., Villard, F., Marsh, M. An automated microseed matrix screening method for protein crystallization, 2007, Acta Crystallographica, D63, 550-554. G. Obmolova, T. J. Malia, A. Teplyakov, R. Sweet and G. L. Gilliland. Promoting crystallization of antibody-antigen complexes via microseed matrix screening Acta Cryst. (2010). D66, 927-933 http://www.douglas.co.uk/mms.htm * * On Tue, Apr 12, 2011 at 1:07 PM, Jun Yong Ha j...@princeton.edu wrote: Hi all, Recently, I produced crystals with MBClass1-64 which contains PEG4000, HEPES-Na and NaCl. But, I struggled to reproduce crystals. I tried to set up tray with different batch of solution. I got the crystals only from 2008 solution, but not from fresh ones. I asked technical service of Qiagen, but they did not have any stock. pH between fresh and old solution is the same. I could reproduce crystals with this old solution 100% when setting up. Do you have any experience like this? Is PEG4000 degraded or oxidized? Please help me. Thanks in advance. -- patr...@douglas.co.ukDouglas Instruments Ltd. DouglasHouse, EastGarston, Hungerford, Berkshire, RG177HD, UK Directors: Peter Baldock, Patrick Shaw Stewart http://www.douglas.co.uk Tel: 44 (0) 148-864-9090US toll-free 1-877-225-2034 Regd. England 2177994, VAT Reg. GB 480 7371 36
Re: [ccp4bb] Comparing two proteins
On 04/13/2011 09:18 PM, REX PALMER wrote: Dear All What is the best program to use for comparing two protein structures which are very similar both structurally and wrt aa sequence? ie to get the rms deviations both generally and in selected regions. Rex Palmer Birkbeck College Using CCP4 go to the coordinate utility Superpose molecules You can either compare things using secondary structure or by specifying residue spans Underlying programs are PISA (also available at the BI msd server) and LSQKAB Eleanor
Re: [ccp4bb] about RMSD bond lengths and angles
See this thread: https://www.jiscmail.ac.uk/cgi-bin/webadmin?A1=ind1009L=CCP4BB#58 Cheers -- Ian On Wed, Apr 13, 2011 at 10:05 PM, Jiamu Du jiam...@gmail.com wrote: Dear All, I am wondering about the ranges of RMSD bond lengths and angles. What are the acceptable ranges for these two values? Is there some statistics for them? Thanks and best wishes.
Re: [ccp4bb] Reproducing crystals.
Hey Jun, If it's an old batch check and see if you have microorganisms living in the stock or proliferating in the drop - see the paper by Bai et al: doi:10.1107/S1744309107002904 In this paper they demonstrated how they could not reproduce a crystal hit from an old screen up until they realized a fungi that grew in the drop has been secreting protease that chewed up certain part of their protein - once they have utilized in-situ proteolysis they managed to reproduce there crystals with their home-made ingredients and, of course, solve the structure. In line with this, and if it is possible, pickup one of those crystals and run it on a gel as they did so to make sure it is in the correct size and not a truncated version. Good luck, Chen --- Chen Guttman The Zarivach laboratory for Macromolecular Crystallography Building 39, Room 009B Ben-Gurion University of the Negev POBox 653 Zip Code 84105 Beer-Sheva Israel http://lifeserv.bgu.ac.il/wb/zarivach Tel. +972-8-6479519 Fax. +972-8-6472970 On Tue, Apr 12, 2011 at 13:56, Jun Yong Ha j...@princeton.edu wrote: Hi all, Recently, I produced crystals with MBClass1-64 which contains PEG4000, HEPES-Na and NaCl. But, I struggled to reproduce crystals. I tried to set up tray with different batch of solution. I got the crystals only from 2008 solution, but not from fresh ones. I asked technical service of Qiagen, but they did not have any stock. pH between fresh and old solution is the same. I could reproduce crystals with this old solution 100% when setting up. Do you have any experience like this? Is PEG4000 degraded or oxidized? Please help me. Thanks in advance.
Re: [ccp4bb] Comparing two proteins
I would like to compare several very similar structures (more than 10) to get the rms deviation over all. Is this possible with any program? Thanks Katie Carr University of Nottingham -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Eleanor Dodson Sent: 14 April 2011 11:51 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Comparing two proteins On 04/13/2011 09:18 PM, REX PALMER wrote: Dear All What is the best program to use for comparing two protein structures which are very similar both structurally and wrt aa sequence? ie to get the rms deviations both generally and in selected regions. Rex Palmer Birkbeck College Using CCP4 go to the coordinate utility Superpose molecules You can either compare things using secondary structure or by specifying residue spans Underlying programs are PISA (also available at the BI msd server) and LSQKAB Eleanor This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please send it back to me, and immediately delete it. Please do not use, copy or disclose the information contained in this message or in any attachment. Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham. This message has been checked for viruses but the contents of an attachment may still contain software viruses which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation.
[ccp4bb] Femtosecond Electron Beam
Dear Crystallographers, is there any reason why we are not considering using super-intense femtosecond electron bursts, instead of photons? Since the scattering of electrons is much more efficient, and because they can be focussed to solve the phase problem, it seems that it might be worthwhile to explore that route of single-molecule structure solution by using electrospray techniques similar to the recently-reported results using the FEL. Is there some technical limitation which would hinder this possibility? JPK -- *** Jacob Pearson Keller Northwestern University Medical Scientist Training Program cel: 773.608.9185 email: j-kell...@northwestern.edu ***
Re: [ccp4bb] NCSMASK question
If you are trying to make a mask in spacegroup P21, that;s not the way
to do it.
Make the mask in NCSMASK without a symmetry keyword. Then run mapmask to
change the spacegroup to P 21 and use EXPAND OVERLAP to generate the
symmetry copies of the mask.
Hailiang Zhang wrote:
Hi,
I want to generate a mask using NCSMASK; however, whenever I tried to add
the SYMMETRY keyword, and output mask cannot be opened in coot. The
following is my script and I was testing on PDB# 2VZ8. Thanks in advance
for any suggestions:
ncsmask xyzin ${EOMDATA}/2VZ8.pdb mskout 2VZ8-ncs.msk eof
SYMMETRY 4
END
eof
Hailiang
--
EMAIL DISCLAIMER http://www.york.ac.uk/docs/disclaimer/email.htm
Re: [ccp4bb] Reproducing crystals.
I once had a similar problem. The crystals only reproduced when grown in condition containing PEG 8000 from SIGMA but not from FLUKA. This difference may not affect crystals from other proteins but some proteins are more sensitive to slight changes than others. Since you found out that the stock is not available, it will be worthwhile to try making stock containing PEG 4000 and maybe also try PEG 4000 from other suppliers. -Raj
[ccp4bb] superpose atom selection
Hello all, from the ccp4 manual: http://www.ccp4.ac.uk/html/superpose.html snip superpose foo_1st.pdb [-s CID1] foo_2nd.pdb [-s CID2] [ foo_out.pdb ] where [-s CID1/2] are optional selection strings in MMDB convention, and [foo_out.pdb] is optional output file. /snip Please, could someone point me to documentation of said MMDB convention. Many thanks in advance, Wolfram Tempel
Re: [ccp4bb] Femtosecond Electron Beam
Jacob Very good question. People are considering this sort of thing. See for example http://www-spires.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-12162.pdf Due to coulomb explosion one normally needs MeV beams to get the short bunch length. MeV beams also give a more reasonable penetration depth (not relevant for single molecules). I think the problem is that the divergence is too high to resolve diffraction spots from protein crystals (or in other words insufficient coherence). Probably fine for many small molecule crystals though. You mentioned single molecules, presumably protein molecules and I think the same would apply if trying to observe the scattering. One could try imaging (i.e. with an electron lens) rather than do diffraction. I presume this is what you mean by focussed to solve the phase problem. However, I understand that there are problems with this as well for MeV beams but I can't remember the exact details. Can look it up if you are interested. There could of course be technical advances which would make some of these ideas possible. I think a group at Eindhoven have plans to get round some of the problems. Again I would have to look up the details. Regards Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Jacob Keller Sent: 14 April 2011 14:39 To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Femtosecond Electron Beam Dear Crystallographers, is there any reason why we are not considering using super-intense femtosecond electron bursts, instead of photons? Since the scattering of electrons is much more efficient, and because they can be focussed to solve the phase problem, it seems that it might be worthwhile to explore that route of single-molecule structure solution by using electrospray techniques similar to the recently-reported results using the FEL. Is there some technical limitation which would hinder this possibility? JPK -- *** Jacob Pearson Keller Northwestern University Medical Scientist Training Program cel: 773.608.9185 email: j-kell...@northwestern.edu ***
Re: [ccp4bb] Comparing two proteins
I have not seen MUSTANG in the list yet. http://pxgrid.med.monash.edu.au:8080/mustangserver/ Jürgen On Apr 14, 2011, at 9:06 AM, Katie Carr wrote: I would like to compare several very similar structures (more than 10) to get the rms deviation over all. Is this possible with any program? Thanks Katie Carr University of Nottingham -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Eleanor Dodson Sent: 14 April 2011 11:51 To: CCP4BB@JISCMAIL.AC.UKmailto:CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Comparing two proteins On 04/13/2011 09:18 PM, REX PALMER wrote: Dear All What is the best program to use for comparing two protein structures which are very similar both structurally and wrt aa sequence? ie to get the rms deviations both generally and in selected regions. Rex Palmer Birkbeck College Using CCP4 go to the coordinate utility Superpose molecules You can either compare things using secondary structure or by specifying residue spans Underlying programs are PISA (also available at the BI msd server) and LSQKAB Eleanor This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please send it back to me, and immediately delete it. Please do not use, copy or disclose the information contained in this message or in any attachment. Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham. This message has been checked for viruses but the contents of an attachment may still contain software viruses which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation. .. Jürgen Bosch Johns Hopkins Bloomberg School of Public Health Department of Biochemistry Molecular Biology Johns Hopkins Malaria Research Institute 615 North Wolfe Street, W8708 Baltimore, MD 21205 Phone: +1-410-614-4742 Lab: +1-410-614-4894 Fax: +1-410-955-3655 http://web.mac.com/bosch_lab/
[ccp4bb] Fwd: superpose atom selection
(Should have) found it! http://www.ccp4.ac.uk/html/pdbcur.html#atom_selection Did not fully RTM. My aplogies. W. -- Forwarded message -- From: goslar gos...@gmail.com Date: Thu, Apr 14, 2011 at 10:19 AM Subject: superpose atom selection To: CCP4BB@jiscmail.ac.uk Hello all, from the ccp4 manual: http://www.ccp4.ac.uk/html/superpose.html snip superpose foo_1st.pdb [-s CID1] foo_2nd.pdb [-s CID2] [ foo_out.pdb ] where [-s CID1/2] are optional selection strings in MMDB convention, and [foo_out.pdb] is optional output file. /snip Please, could someone point me to documentation of said MMDB convention. Many thanks in advance, Wolfram Tempel
Re: [ccp4bb] Femtosecond Electron Beam
People are looking into how to fit the old retired MeV microscopes with pulsed electron guns (problem is there are very few of those beasts left). If this works, such a machine will produce equivalent results to FEL but at a fraction of the cost. The group at Eindhoven, which Colin had mentioned, has already made a significant progress in achieving both time and spatial coherence. They are able to manipulate electrons in ultrashort electron bunches akin to spins in an NMR machine: http://prl.aps.org/abstract/PRL/v105/i26/e264801 http://jap.aip.org/resource/1/japiau/v109/i3/p033302_s1 And this is due to the fact that electrons can be focused with lenses. Amazing stuff. We will hear more about this for sure. Sincerely, Petr From: CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] on behalf of Colin Nave [colin.n...@diamond.ac.uk] Sent: Thursday, April 14, 2011 16:50 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam Jacob Very good question. People are considering this sort of thing. See for example http://www-spires.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-12162.pdf Due to coulomb explosion one normally needs MeV beams to get the short bunch length. MeV beams also give a more reasonable penetration depth (not relevant for single molecules). I think the problem is that the divergence is too high to resolve diffraction spots from protein crystals (or in other words insufficient coherence). Probably fine for many small molecule crystals though. You mentioned single molecules, presumably protein molecules and I think the same would apply if trying to observe the scattering. One could try imaging (i.e. with an electron lens) rather than do diffraction. I presume this is what you mean by focussed to solve the phase problem. However, I understand that there are problems with this as well for MeV beams but I can't remember the exact details. Can look it up if you are interested. There could of course be technical advances which would make some of these ideas possible. I think a group at Eindhoven have plans to get round some of the problems. Again I would have to look up the details. Regards Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Jacob Keller Sent: 14 April 2011 14:39 To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Femtosecond Electron Beam Dear Crystallographers, is there any reason why we are not considering using super-intense femtosecond electron bursts, instead of photons? Since the scattering of electrons is much more efficient, and because they can be focussed to solve the phase problem, it seems that it might be worthwhile to explore that route of single-molecule structure solution by using electrospray techniques similar to the recently-reported results using the FEL. Is there some technical limitation which would hinder this possibility? JPK -- *** Jacob Pearson Keller Northwestern University Medical Scientist Training Program cel: 773.608.9185 email: j-kell...@northwestern.edu ***
Re: [ccp4bb] Fwd: superpose atom selection
Only bear in mind that superpose relies on the presence of secondary structure, so that your selections should always include at least 3 SSEs. Eugene. On 14 Apr 2011, at 15:45, goslar wrote: (Should have) found it! http://www.ccp4.ac.uk/html/pdbcur.html#atom_selection Did not fully RTM. My aplogies. W. -- Forwarded message -- From: goslar gos...@gmail.com Date: Thu, Apr 14, 2011 at 10:19 AM Subject: superpose atom selection To: CCP4BB@jiscmail.ac.uk Hello all, from the ccp4 manual: http://www.ccp4.ac.uk/html/superpose.html snip superpose foo_1st.pdb [-s CID1] foo_2nd.pdb [-s CID2] [ foo_out.pdb ] where [-s CID1/2] are optional selection strings in MMDB convention, and [foo_out.pdb] is optional output file. /snip Please, could someone point me to documentation of said MMDB convention. Many thanks in advance, Wolfram Tempel
Re: [ccp4bb] Femtosecond Electron Beam
Dear Jacob, Ahmed Zewail's papers are worth consulting on this, although not protein/bio. See also the book by Zewail and Thomas, recently published, easily findable on amazon etc, as a handy overview. Best wishes, John Prof John R Helliwell DSc On 14 Apr 2011, at 14:38, Jacob Keller j-kell...@fsm.northwestern.edu wrote: Dear Crystallographers, is there any reason why we are not considering using super-intense femtosecond electron bursts, instead of photons? Since the scattering of electrons is much more efficient, and because they can be focussed to solve the phase problem, it seems that it might be worthwhile to explore that route of single-molecule structure solution by using electrospray techniques similar to the recently-reported results using the FEL. Is there some technical limitation which would hinder this possibility? JPK -- *** Jacob Pearson Keller Northwestern University Medical Scientist Training Program cel: 773.608.9185 email: j-kell...@northwestern.edu ***
Re: [ccp4bb] NCSMASK question
Thanks a lot!
If you are trying to make a mask in spacegroup P21, that;s not the way
to do it.
Make the mask in NCSMASK without a symmetry keyword. Then run mapmask to
change the spacegroup to P 21 and use EXPAND OVERLAP to generate the
symmetry copies of the mask.
Hailiang Zhang wrote:
Hi,
I want to generate a mask using NCSMASK; however, whenever I tried to
add
the SYMMETRY keyword, and output mask cannot be opened in coot. The
following is my script and I was testing on PDB# 2VZ8. Thanks in advance
for any suggestions:
ncsmask xyzin ${EOMDATA}/2VZ8.pdb mskout 2VZ8-ncs.msk eof
SYMMETRY 4
END
eof
Hailiang
--
EMAIL DISCLAIMER http://www.york.ac.uk/docs/disclaimer/email.htm
[ccp4bb] reference on the van der Waals contact distance
Hello, I often see these vdW contact distance cut-off numbers (see below) in papers, but no reference was given. Contact distances are the following maximum allowed values: C-C, 4.1 Å; C-N, 3.8 Å; C-O, 3.7 Å; O-O, 3.3 Å; O-N, 3.4 Å; N-N, 3.4 Å; C-S, 4.1 Å; O-S, 3.7 Å; N-S, 3.8 Å. I am curious how these numbers were developed. For example, S has a larger vdW radius than C, but the vdW contact cut-offs are the same as for C. Does any one know such an old reference or textbook for these numbers? Thanks Rongjin Guan
Re: [ccp4bb] Femtosecond Electron Beam
Petr has provided the Eindhoven links. For more details on fast electron imaging (as opposed to diffraction) see https://e-reports-ext.llnl.gov/pdf/343044.pdf Apparently stochastic scattering of the electrons at the high current densities necessary for short pulsed sources result in blurring in the image. The paper says that 10nm spatial and 10ps temporal resolution could be achieved with 5MeV electrons and annular dark field imaging. Of course more recent developments at Eindhoven and elsewhere might get round some of the limitations. Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Petr Leiman Sent: 14 April 2011 16:23 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam People are looking into how to fit the old retired MeV microscopes with pulsed electron guns (problem is there are very few of those beasts left). If this works, such a machine will produce equivalent results to FEL but at a fraction of the cost. The group at Eindhoven, which Colin had mentioned, has already made a significant progress in achieving both time and spatial coherence. They are able to manipulate electrons in ultrashort electron bunches akin to spins in an NMR machine: http://prl.aps.org/abstract/PRL/v105/i26/e264801 http://jap.aip.org/resource/1/japiau/v109/i3/p033302_s1 And this is due to the fact that electrons can be focused with lenses. Amazing stuff. We will hear more about this for sure. Sincerely, Petr From: CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] on behalf of Colin Nave [colin.n...@diamond.ac.uk] Sent: Thursday, April 14, 2011 16:50 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam Jacob Very good question. People are considering this sort of thing. See for example http://www-spires.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-12162.pdf Due to coulomb explosion one normally needs MeV beams to get the short bunch length. MeV beams also give a more reasonable penetration depth (not relevant for single molecules). I think the problem is that the divergence is too high to resolve diffraction spots from protein crystals (or in other words insufficient coherence). Probably fine for many small molecule crystals though. You mentioned single molecules, presumably protein molecules and I think the same would apply if trying to observe the scattering. One could try imaging (i.e. with an electron lens) rather than do diffraction. I presume this is what you mean by focussed to solve the phase problem. However, I understand that there are problems with this as well for MeV beams but I can't remember the exact details. Can look it up if you are interested. There could of course be technical advances which would make some of these ideas possible. I think a group at Eindhoven have plans to get round some of the problems. Again I would have to look up the details. Regards Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Jacob Keller Sent: 14 April 2011 14:39 To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Femtosecond Electron Beam Dear Crystallographers, is there any reason why we are not considering using super-intense femtosecond electron bursts, instead of photons? Since the scattering of electrons is much more efficient, and because they can be focussed to solve the phase problem, it seems that it might be worthwhile to explore that route of single-molecule structure solution by using electrospray techniques similar to the recently-reported results using the FEL. Is there some technical limitation which would hinder this possibility? JPK -- *** Jacob Pearson Keller Northwestern University Medical Scientist Training Program cel: 773.608.9185 email: j-kell...@northwestern.edu ***
Re: [ccp4bb] Femtosecond Electron Beam
Dear Colin and all interested in the FEL development. Please look at the figures in the first link I mentioned. Jom Luiten et al. are able to record a 1.25 A resolution diffraction pattern of a gold foil using a pulse compressed to 50 fs. Ahmed Zewail is a pioneer of the technique but as far as I know his instrumentation is nowhere near Jom's amazing machine. Why Jom's paper was not published in one of the high profile journals, ahem, magazines, is a mystery to me. Petr On Apr 14, 2011, at 9:11 PM, Colin Nave wrote: Petr has provided the Eindhoven links. For more details on fast electron imaging (as opposed to diffraction) see https://e-reports-ext.llnl.gov/pdf/343044.pdf Apparently stochastic scattering of the electrons at the high current densities necessary for short pulsed sources result in blurring in the image. The paper says that 10nm spatial and 10ps temporal resolution could be achieved with 5MeV electrons and annular dark field imaging. Of course more recent developments at Eindhoven and elsewhere might get round some of the limitations. Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Petr Leiman Sent: 14 April 2011 16:23 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam People are looking into how to fit the old retired MeV microscopes with pulsed electron guns (problem is there are very few of those beasts left). If this works, such a machine will produce equivalent results to FEL but at a fraction of the cost. The group at Eindhoven, which Colin had mentioned, has already made a significant progress in achieving both time and spatial coherence. They are able to manipulate electrons in ultrashort electron bunches akin to spins in an NMR machine: http://prl.aps.org/abstract/PRL/v105/i26/e264801 http://jap.aip.org/resource/1/japiau/v109/i3/p033302_s1 And this is due to the fact that electrons can be focused with lenses. Amazing stuff. We will hear more about this for sure. Sincerely, Petr From: CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] on behalf of Colin Nave [colin.n...@diamond.ac.uk] Sent: Thursday, April 14, 2011 16:50 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam Jacob Very good question. People are considering this sort of thing. See for example http://www-spires.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-12162.pdf Due to coulomb explosion one normally needs MeV beams to get the short bunch length. MeV beams also give a more reasonable penetration depth (not relevant for single molecules). I think the problem is that the divergence is too high to resolve diffraction spots from protein crystals (or in other words insufficient coherence). Probably fine for many small molecule crystals though. You mentioned single molecules, presumably protein molecules and I think the same would apply if trying to observe the scattering. One could try imaging (i.e. with an electron lens) rather than do diffraction. I presume this is what you mean by focussed to solve the phase problem. However, I understand that there are problems with this as well for MeV beams but I can't remember the exact details. Can look it up if you are interested. There could of course be technical advances which would make some of these ideas possible. I think a group at Eindhoven have plans to get round some of the problems. Again I would have to look up the details. Regards Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Jacob Keller Sent: 14 April 2011 14:39 To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Femtosecond Electron Beam Dear Crystallographers, is there any reason why we are not considering using super-intense femtosecond electron bursts, instead of photons? Since the scattering of electrons is much more efficient, and because they can be focussed to solve the phase problem, it seems that it might be worthwhile to explore that route of single-molecule structure solution by using electrospray techniques similar to the recently-reported results using the FEL. Is there some technical limitation which would hinder this possibility? JPK -- *** Jacob Pearson Keller Northwestern University Medical Scientist Training Program cel: 773.608.9185 email: j-kell...@northwestern.edu ***
Re: [ccp4bb] Femtosecond Electron Beam
Petr Yes, I saw the figure. Similar ones appear in the Hastings et. al. paper (the SLAC one I referenced). They use a much higher energy beam to get the short pulse length. I still believe the issues are 1. For diffraction, can you get a low enough electron beam divergence to resolve larger unit cells? The peaks appear rather broad in the foil experiments. Luiten et. al. believe they can extend the technique to resolve cells of a few tens of nm which would be fine. Their ideas for doing this appear to be quite novel. I don't know if they have demonstrated this though. 2. Given the above, will there be enough electrons in one of the short pulses to get enough statistics for a biological molecule or protein nano-crystal? I have not seen calculations for this for electron beams (as has been done for the FEL x-ray beams). Actually it should be quite easy to do as the cross sections are all available. 3. For imaging (i.e. using an objective lens) is the blurring I mention going to be a fundamental limitation and what will this limitation be? These instruments would be useful for material science applications and fast chemistry investigations where some of the above issues would not be relevant. Not sure for imaging biological molecules. We will see. Finally saying Phys Rev Let is not a high impact journal would probably upset my physicist colleagues - that's fine though! Regards Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Petr Leiman Sent: 14 April 2011 21:07 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam Dear Colin and all interested in the FEL development. Please look at the figures in the first link I mentioned. Jom Luiten et al. are able to record a 1.25 A resolution diffraction pattern of a gold foil using a pulse compressed to 50 fs. Ahmed Zewail is a pioneer of the technique but as far as I know his instrumentation is nowhere near Jom's amazing machine. Why Jom's paper was not published in one of the high profile journals, ahem, magazines, is a mystery to me. Petr On Apr 14, 2011, at 9:11 PM, Colin Nave wrote: Petr has provided the Eindhoven links. For more details on fast electron imaging (as opposed to diffraction) see https://e-reports-ext.llnl.gov/pdf/343044.pdf Apparently stochastic scattering of the electrons at the high current densities necessary for short pulsed sources result in blurring in the image. The paper says that 10nm spatial and 10ps temporal resolution could be achieved with 5MeV electrons and annular dark field imaging. Of course more recent developments at Eindhoven and elsewhere might get round some of the limitations. Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Petr Leiman Sent: 14 April 2011 16:23 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam People are looking into how to fit the old retired MeV microscopes with pulsed electron guns (problem is there are very few of those beasts left). If this works, such a machine will produce equivalent results to FEL but at a fraction of the cost. The group at Eindhoven, which Colin had mentioned, has already made a significant progress in achieving both time and spatial coherence. They are able to manipulate electrons in ultrashort electron bunches akin to spins in an NMR machine: http://prl.aps.org/abstract/PRL/v105/i26/e264801 http://jap.aip.org/resource/1/japiau/v109/i3/p033302_s1 And this is due to the fact that electrons can be focused with lenses. Amazing stuff. We will hear more about this for sure. Sincerely, Petr From: CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] on behalf of Colin Nave [colin.n...@diamond.ac.uk] Sent: Thursday, April 14, 2011 16:50 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam Jacob Very good question. People are considering this sort of thing. See for example http://www-spires.slac.stanford.edu/cgi-wrap/getdoc/slac-pub- 12162.pdf Due to coulomb explosion one normally needs MeV beams to get the short bunch length. MeV beams also give a more reasonable penetration depth (not relevant for single molecules). I think the problem is that the divergence is too high to resolve diffraction spots from protein crystals (or in other words insufficient coherence). Probably fine for many small molecule crystals though. You mentioned single molecules, presumably protein molecules and I think the same would apply if trying to observe the scattering. One could try imaging (i.e. with an electron lens) rather than do diffraction. I presume this is what you mean by focussed to solve the phase problem. However, I understand that there are problems with this as well for MeV beams but I can't remember the
Re: [ccp4bb] Femtosecond Electron Beam
Colin, We know that with a dose of 20-30 electrons per A^2, a lot of image processing, and insane amount of luck, one can reconstruct cryoEM images to 3 A resolution or better. A typical protein molecule is say 100 A in diameter, which is ~8000 A^2 in projection. So, in an ideal case one needs only 240,000 electrons to record an image of a protein molecule with a signal extending to 3A resolution. Jacob, Yes, you are correct. Jom et al. manipulate electron bunches of 1+ Mln electrons, which should be enough to record an image of a protein molecule. Best, Petr On Apr 14, 2011, at 11:13 PM, Colin Nave wrote: Petr Yes, I saw the figure. Similar ones appear in the Hastings et. al. paper (the SLAC one I referenced). They use a much higher energy beam to get the short pulse length. I still believe the issues are 1. For diffraction, can you get a low enough electron beam divergence to resolve larger unit cells? The peaks appear rather broad in the foil experiments. Luiten et. al. believe they can extend the technique to resolve cells of a few tens of nm which would be fine. Their ideas for doing this appear to be quite novel. I don't know if they have demonstrated this though. 2. Given the above, will there be enough electrons in one of the short pulses to get enough statistics for a biological molecule or protein nano-crystal? I have not seen calculations for this for electron beams (as has been done for the FEL x-ray beams). Actually it should be quite easy to do as the cross sections are all available. 3. For imaging (i.e. using an objective lens) is the blurring I mention going to be a fundamental limitation and what will this limitation be? These instruments would be useful for material science applications and fast chemistry investigations where some of the above issues would not be relevant. Not sure for imaging biological molecules. We will see. Finally saying Phys Rev Let is not a high impact journal would probably upset my physicist colleagues - that's fine though! Regards Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Petr Leiman Sent: 14 April 2011 21:07 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam Dear Colin and all interested in the FEL development. Please look at the figures in the first link I mentioned. Jom Luiten et al. are able to record a 1.25 A resolution diffraction pattern of a gold foil using a pulse compressed to 50 fs. Ahmed Zewail is a pioneer of the technique but as far as I know his instrumentation is nowhere near Jom's amazing machine. Why Jom's paper was not published in one of the high profile journals, ahem, magazines, is a mystery to me. Petr On Apr 14, 2011, at 9:11 PM, Colin Nave wrote: Petr has provided the Eindhoven links. For more details on fast electron imaging (as opposed to diffraction) see https://e-reports-ext.llnl.gov/pdf/343044.pdf Apparently stochastic scattering of the electrons at the high current densities necessary for short pulsed sources result in blurring in the image. The paper says that 10nm spatial and 10ps temporal resolution could be achieved with 5MeV electrons and annular dark field imaging. Of course more recent developments at Eindhoven and elsewhere might get round some of the limitations. Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Petr Leiman Sent: 14 April 2011 16:23 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam People are looking into how to fit the old retired MeV microscopes with pulsed electron guns (problem is there are very few of those beasts left). If this works, such a machine will produce equivalent results to FEL but at a fraction of the cost. The group at Eindhoven, which Colin had mentioned, has already made a significant progress in achieving both time and spatial coherence. They are able to manipulate electrons in ultrashort electron bunches akin to spins in an NMR machine: http://prl.aps.org/abstract/PRL/v105/i26/e264801 http://jap.aip.org/resource/1/japiau/v109/i3/p033302_s1 And this is due to the fact that electrons can be focused with lenses. Amazing stuff. We will hear more about this for sure. Sincerely, Petr From: CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] on behalf of Colin Nave [colin.n...@diamond.ac.uk] Sent: Thursday, April 14, 2011 16:50 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam Jacob Very good question. People are considering this sort of thing. See for example http://www-spires.slac.stanford.edu/cgi-wrap/getdoc/slac-pub- 12162.pdf Due to coulomb explosion one normally needs MeV beams to get the short bunch length. MeV beams also give a more reasonable penetration depth (not relevant for single
Re: [ccp4bb] Femtosecond Electron Beam
Petr Well, not sure - are we doing imaging or diffraction/scattering? What energy are the electrons in these sources? The idea of pulsed sources is to put more electrons/A^2 and still beat radiation damage. Can one do this when there are only around 10^6 electrons in perhaps a rather divergent beam? Shall we discuss off line (with Jacob) and present our conclusions when/if we get agreement? Regards Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Petr Leiman Sent: 14 April 2011 22:59 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam Colin, We know that with a dose of 20-30 electrons per A^2, a lot of image processing, and insane amount of luck, one can reconstruct cryoEM images to 3 A resolution or better. A typical protein molecule is say 100 A in diameter, which is ~8000 A^2 in projection. So, in an ideal case one needs only 240,000 electrons to record an image of a protein molecule with a signal extending to 3A resolution. Jacob, Yes, you are correct. Jom et al. manipulate electron bunches of 1+ Mln electrons, which should be enough to record an image of a protein molecule. Best, Petr On Apr 14, 2011, at 11:13 PM, Colin Nave wrote: Petr Yes, I saw the figure. Similar ones appear in the Hastings et. al. paper (the SLAC one I referenced). They use a much higher energy beam to get the short pulse length. I still believe the issues are 1. For diffraction, can you get a low enough electron beam divergence to resolve larger unit cells? The peaks appear rather broad in the foil experiments. Luiten et. al. believe they can extend the technique to resolve cells of a few tens of nm which would be fine. Their ideas for doing this appear to be quite novel. I don't know if they have demonstrated this though. 2. Given the above, will there be enough electrons in one of the short pulses to get enough statistics for a biological molecule or protein nano-crystal? I have not seen calculations for this for electron beams (as has been done for the FEL x-ray beams). Actually it should be quite easy to do as the cross sections are all available. 3. For imaging (i.e. using an objective lens) is the blurring I mention going to be a fundamental limitation and what will this limitation be? These instruments would be useful for material science applications and fast chemistry investigations where some of the above issues would not be relevant. Not sure for imaging biological molecules. We will see. Finally saying Phys Rev Let is not a high impact journal would probably upset my physicist colleagues - that's fine though! Regards Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Petr Leiman Sent: 14 April 2011 21:07 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam Dear Colin and all interested in the FEL development. Please look at the figures in the first link I mentioned. Jom Luiten et al. are able to record a 1.25 A resolution diffraction pattern of a gold foil using a pulse compressed to 50 fs. Ahmed Zewail is a pioneer of the technique but as far as I know his instrumentation is nowhere near Jom's amazing machine. Why Jom's paper was not published in one of the high profile journals, ahem, magazines, is a mystery to me. Petr On Apr 14, 2011, at 9:11 PM, Colin Nave wrote: Petr has provided the Eindhoven links. For more details on fast electron imaging (as opposed to diffraction) see https://e-reports-ext.llnl.gov/pdf/343044.pdf Apparently stochastic scattering of the electrons at the high current densities necessary for short pulsed sources result in blurring in the image. The paper says that 10nm spatial and 10ps temporal resolution could be achieved with 5MeV electrons and annular dark field imaging. Of course more recent developments at Eindhoven and elsewhere might get round some of the limitations. Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Petr Leiman Sent: 14 April 2011 16:23 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam People are looking into how to fit the old retired MeV microscopes with pulsed electron guns (problem is there are very few of those beasts left). If this works, such a machine will produce equivalent results to FEL but at a fraction of the cost. The group at Eindhoven, which Colin had mentioned, has already made a significant progress in achieving both time and spatial coherence. They are able to manipulate electrons in ultrashort electron bunches akin to spins in an NMR machine: http://prl.aps.org/abstract/PRL/v105/i26/e264801 http://jap.aip.org/resource/1/japiau/v109/i3/p033302_s1 And this is due to the fact that electrons can be
Re: [ccp4bb] Femtosecond Electron Beam
One of the figures they cite is 2.5 electrons per um^2, which I think means once the whole bunch has gone through. That struck me as being pretty far from where one needs to be to get structures. Do you know off hand a comparable figure for the FEL experiment? I assume it would be many orders of magnitude greater. For example, how many total photons were in each bunch with the FEL? JPK On Thu, Apr 14, 2011 at 5:24 PM, Colin Nave colin.n...@diamond.ac.uk wrote: Petr Well, not sure - are we doing imaging or diffraction/scattering? What energy are the electrons in these sources? The idea of pulsed sources is to put more electrons/A^2 and still beat radiation damage. Can one do this when there are only around 10^6 electrons in perhaps a rather divergent beam? Shall we discuss off line (with Jacob) and present our conclusions when/if we get agreement? Regards Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Petr Leiman Sent: 14 April 2011 22:59 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam Colin, We know that with a dose of 20-30 electrons per A^2, a lot of image processing, and insane amount of luck, one can reconstruct cryoEM images to 3 A resolution or better. A typical protein molecule is say 100 A in diameter, which is ~8000 A^2 in projection. So, in an ideal case one needs only 240,000 electrons to record an image of a protein molecule with a signal extending to 3A resolution. Jacob, Yes, you are correct. Jom et al. manipulate electron bunches of 1+ Mln electrons, which should be enough to record an image of a protein molecule. Best, Petr On Apr 14, 2011, at 11:13 PM, Colin Nave wrote: Petr Yes, I saw the figure. Similar ones appear in the Hastings et. al. paper (the SLAC one I referenced). They use a much higher energy beam to get the short pulse length. I still believe the issues are 1. For diffraction, can you get a low enough electron beam divergence to resolve larger unit cells? The peaks appear rather broad in the foil experiments. Luiten et. al. believe they can extend the technique to resolve cells of a few tens of nm which would be fine. Their ideas for doing this appear to be quite novel. I don't know if they have demonstrated this though. 2. Given the above, will there be enough electrons in one of the short pulses to get enough statistics for a biological molecule or protein nano-crystal? I have not seen calculations for this for electron beams (as has been done for the FEL x-ray beams). Actually it should be quite easy to do as the cross sections are all available. 3. For imaging (i.e. using an objective lens) is the blurring I mention going to be a fundamental limitation and what will this limitation be? These instruments would be useful for material science applications and fast chemistry investigations where some of the above issues would not be relevant. Not sure for imaging biological molecules. We will see. Finally saying Phys Rev Let is not a high impact journal would probably upset my physicist colleagues - that's fine though! Regards Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Petr Leiman Sent: 14 April 2011 21:07 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam Dear Colin and all interested in the FEL development. Please look at the figures in the first link I mentioned. Jom Luiten et al. are able to record a 1.25 A resolution diffraction pattern of a gold foil using a pulse compressed to 50 fs. Ahmed Zewail is a pioneer of the technique but as far as I know his instrumentation is nowhere near Jom's amazing machine. Why Jom's paper was not published in one of the high profile journals, ahem, magazines, is a mystery to me. Petr On Apr 14, 2011, at 9:11 PM, Colin Nave wrote: Petr has provided the Eindhoven links. For more details on fast electron imaging (as opposed to diffraction) see https://e-reports-ext.llnl.gov/pdf/343044.pdf Apparently stochastic scattering of the electrons at the high current densities necessary for short pulsed sources result in blurring in the image. The paper says that 10nm spatial and 10ps temporal resolution could be achieved with 5MeV electrons and annular dark field imaging. Of course more recent developments at Eindhoven and elsewhere might get round some of the limitations. Colin -Original Message- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Petr Leiman Sent: 14 April 2011 16:23 To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Femtosecond Electron Beam People are looking into how to fit the old retired MeV microscopes with pulsed electron guns (problem is there are very few of those beasts left). If this works, such a machine will produce equivalent
