Hi Alex,
Although there is an “ice” icon in the imosflm GUI, which excludes
all resolution bins where ice ringss are possible, this is not the best way to
deal with this. Instead, use the Settings -> Processing options -> Processing
tab, where you can specify individual resolution ranges to be excluded from the
integration.
The important thing here is to make sure that the resolution range you specify
is generous enough. Looking at an image and holding down the Ctrl key to give
you the resolution where the mouse pointer is positioned, you need to make sure
that you specify resolution limits that are a bit below (on the low resolution
side) and above (on the high resolution side) the ice ring itself. This is
because if any part of the measurement box extends into the ice ring it can
affect the integration, and the measurement box is larger than the actual spot
size.
This will, of course, affect your overall completeness, but it should get rid
of the reflections with anomalous intensity. I find that the easiest way to
check this is to look at the Wilson plot produced by ctruncate (one of the post
you get when you run QuickScale).
Best wishes,
Andrew
> On 4 Mar 2021, at 15:39, Alexander Brown <[email protected]>
> wrote:
>
> Hi all,
> I'm struggling with a dataset I have which shows very poor data quality
> around 3.6A, or exactly where I can see a significant ice ring in the images.
> I'm trying to use mosflm to process the image files, and I have seen a
> previous thread on the message board where it is recommended to turn on three
> tick boxes for ice ring exclusion, but despite this, as I continue through
> the processing sequence and use aimless, it still flags that the data is
> affected by an ice ring at that resolution, which you can also see in the
> quality/resolution graphs.
>
> I have even tried making a mask in the moslfm viewer using the mask tool to
> cover the entire ice ring, but to no avail.
>
> Finally I did have a go at using EVAL which is mentioned in the original post
> about ice rings, but it seems it depends on libgfortran3 packages which have
> now been replaced with libgfortran5 and so I didn't get very far.
>
> Is there a manual way to mask out certain data, or could there be something
> with my data that is causing the automatic ice ring resolution not to be as
> effective?
>
> Thank you!
>
> Alex Brown
>
> PhD Student
> School of Pharmacy
> Biodiscovery Institute (previously Centre for Biomolecular sciences)
> University of Nottingham
> Nottingham
> NG7 2RD
>
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