Remote Operation
As of summer 2009, remote data collection will be possible. Samples sent by post/courier service will be received and mounted at the sample changer by beamline staff. The data collection and analysis will be done by the users over NX Client, a free program available for all major platforms.
Special requirements
Remote operation will be performed only on fully prepared samples that require no on-site manipulations. In addition, samples that cannot be loaded with the sample changer (viscous or foaming solutions) will not be measured. The samples should be placed into 96 well plates or stripes of PCR-tubes, while buffers should be provided in 1.5 ml tubes. The sample descriptions should be provided in an Excel spreadsheet. The only on-site operation which the beamline stuff will perform is centrifugation before the experiment. Please find the information about sending your samples below.
The sample concentrations must be determined as precise as possible (accuracy better than 10% is required). The concentrations are necessary to normalize the scattering data. Bradford assays are usually not sufficiently precise, OD measurements @280 nm are better. A single SAXS measurement in automated mode requires about 90 μl of sample, and the exposure is about 2 minutes. The samples can be damaged by synchrotron radiation during the collection time. A reducing agent (e.g. 2mM DTT) is typically added to the sample before the experiment to diminish the damage/aggregation during the data collection.
Each measurement of the macromolecular solution requires two measurements of the corresponding buffer (before and after the sample). You should send sufficient amount (> 10 ml) of matching buffer(s). The buffers should not contain excessive amounts of additives (e.g. not more than 0.5M NaCl, not more than 5% glycerol, not more than 5 mM ATP etc) unless this is unavoidable. If you need to work with the buffers containing excessive amounts of additives, please consult us in advance. Typically, for each sample a concentration series (e.g. 1, 2, 5, 10 mg/ml) has to be measured. The cell is cleaned and refilled automatically/manually after each measurement.
The users must verify the sample monodispersity (desirably > 90%) e.g. by native gel filtration, ultracentrifugation, DLS etc. If the sample is aggregated, the scattering data will be difficult or even impossible to interpret. Please note that a single band on the SDS gel goes not indicate monodisperse solutions – a single band on the native gel is required!