What about the recently-published engineered DNA crystal: Nature. 2009 Sep 3;461(7260):74-7. >From molecular to macroscopic via the rational design of a self-assembled 3D DNA crystal. Zheng J, Birktoft JJ, Chen Y, Wang T, Sha R, Constantinou PE, Ginell SL, Mao C, Seeman NC. Source Department of Chemistry, New York University, New York 10003, USA. Abstract We live in a macroscopic three-dimensional (3D) world, but our best description of the structure of matter is at the atomic and molecular scale. Understanding the relationship between the two scales requires a bridge from the molecular world to the macroscopic world. Connecting these two domains with atomic precision is a central goal of the natural sciences, but it requires high spatial control of the 3D structure of matter. The simplest practical route to producing precisely designed 3D macroscopic objects is to form a crystalline arrangement by self-assembly, because such a periodic array has only conceptually simple requirements: a motif that has a robust 3D structure, dominant affinity interactions between parts of the motif when it self-associates, and predictable structures for these affinity interactions. Fulfilling these three criteria to produce a 3D periodic system is not easy, but should readily be achieved with well-structured branched DNA motifs tailed by sticky ends. Complementary sticky ends associate with each other preferentially and assume the well-known B-DNA structure when they do so; the helically repeating nature of DNA facilitates the construction of a periodic array. It is essential that the directions of propagation associated with the sticky ends do not share the same plane, but extend to form a 3D arrangement of matter. Here we report the crystal structure at 4 A resolution of a designed, self-assembled, 3D crystal based on the DNA tensegrity triangle. The data demonstrate clearly that it is possible to design and self-assemble a well-ordered macromolecular 3D crystalline lattice with precise control.
PMID: 19727196 [PubMed - indexed for MEDLINE] PMCID: PMC2764300 Free PMC Article On Wed, Jun 29, 2011 at 7:42 PM, Michael Thompson <[email protected]> wrote: > Hi Paul, > > While crystal contacts are typically of a non-covalent nature, there are some > exceptions. A disulfide bond can act as a crystal contact, which is a > covalent interaction. A technique called synthetic symmetrization involves > the engineering of single cysteine mutants, followed by oxidation to form an > intermolecular disulfide bond that lies on a 2-fold symmetry axis between the > two monomers. The original goal of this technique was to turn an asymmetric > monomer into a symmetric dimer, which should crystallize more readily if the > artificial 2-fold lies on a crystallographic symmetry axis. Recently, a paper > illustrated that even if the artificial 2-fold axis does not become a > crystallographic axis, the introduction of a disulfide can create artificial > "crystal contacts," which also aid in crystallization. Check out the > following paper. There is a nice figure that shows two protein molecules that > are really not touching with the exception of the engineered disulfide bond > that forms the only contact. > > Protein Sci. 2011 Jan;20(1):168-78. > Synthetic symmetrization in the crystallization and structure determination > of CelA from Thermotoga maritima. > > HTH, > > Mike > > > > > ----- Original Message ----- > From: "Paul Lindblom" <[email protected]> > To: [email protected] > Sent: Wednesday, June 29, 2011 2:22:26 PM GMT -08:00 US/Canada Pacific > Subject: [ccp4bb] The Good and the Bad crystal contact? > > Hi everybody, > > can anybody tell me how crystal contacts are defined? Are there good and bad > crystal contacts? They are the most important interactions with impact on the > crystal quality, but they are not of covalent nature, aren´t they? > > With best regards, > > Paul > > -- > Michael C. Thompson > > Graduate Student > > Biochemistry & Molecular Biology Division > > Department of Chemistry & Biochemistry > > University of California, Los Angeles > > [email protected] > -- ******************************************* Jacob Pearson Keller Northwestern University Medical Scientist Training Program cel: 773.608.9185 email: [email protected] *******************************************
