Results tagged “PX” from The SIBYLS Beamline

A frustrating challenge faced by crystallographers is the often futile and time consuming effort spent improving the resolution of poorly diffracting crystals for complexes. Most efforts to improve diffraction are carried out in the wet lab and entail modifications to sample preparation, crystal growth, and crystal harvesting. Currently, there are few technologies available to improve crystal diffraction quality at the synchrotron. However, the solvent content in protein crystals varies from 30% to 70%, and experiments have shown that humidity changes are correlated with defined (and reversible) unit cell adjustments. Robert Huber’s group developed a revolutionary technology for MX: the Free Mounting Device (FMD), which can manipulate the humidity environment around protein crystals in a controlled and reproducible manner and then allow measurement of diffraction quality as a function of humidity 1. The SIBYLS beamline has the first publicly available FMD system in the world. An example of a result made possible by the FMD was the determination of the crystal structure of the catalytic α subunit of E. Coli DNA polymerase III to 2.3Å resolution2. The previous best resolution was ~3Å and contained disordered domains which became ordered upon dehydration.

FMD - Main Humidty Control Unit

fmd_1.jpg

FMD - “Iron Maiden”

fmd_2.jpg fmd_3.jpg

Here is the FMD Iron Maiden on the microscope stand, ready for crystal harvesting.

fmd_4.jpg

… and on the goniometer.

fmd_5.jpg

FMD - Control Software

This is a screenshot of the software for programming in precise humidty ramps.

fmd_6.jpg

footnotes

  1. Kiefersauer R, Than ME, Dobbek H, Gremer L, Melero M, Strobl S, Dias JM, Soulimane T, and Huber R “A novel free-mounting system for protein crystals: transformation and improvement of diffraction power by accurately controlled humidity changes” J. Appl. Cryst. (2000). 33, 1223-1230

  2. Lamers MH, Georgescu RE, Lee SG, O’Donnell M, Kuriyan J “Crystal structure of the catalytic alpha subunit of E. coli replicative DNA polymerase III” Cell. 2006 Sep 8;126(5):881-92.
    link out

For the MX endstation we've characterized the dependence of the direct beam on detector distance and 2-theta. We collected 4 sweeps of the detector from 120mm to 1600mm combined with 2-theta offsets from 0º up to 12º. These are the gnuplot 3D plots of the data.
xbeams.png ybeams.png
This set of 3D plots uses gnuplots pm3d settings to generate colorful versions:
xbeam3ds.png ybeam3ds.png
Click the images to view larger versions, and hit the "jump" to read the gory details of the polynomial equation used to determine x-beam and y-beam given any value of detector distance (CCD_Z) and 2-theta.

A paper has been published in The October 2 issue of Cell by Scott Williams et al. that sheds light on a previously missing piece of the double-strand break repair complex MRN (aka Mre11-Rad50-Nbs1). The paper entitled “Nbs1 Flexibly Tethers Ctp1 and Mre11-Rad50 to Coordinate DNA Double-Strand Break Processing and Repair” presents a compelling model of the role of Nbs1 (i.e “N” of the MRN) in coordinating double-strand break processing and repair. The paper was made possible in part by crystal structures and SAXS data of Nbs1 that were collected at the SIBYLS beamline.

MRN_model.png

Abstract:

The Nijmegen breakage syndrome 1 (Nbs1) subunit of the Mre11-Rad50-Nbs1 (MRN) complex protects genome integrity by coordinating double-strand break (DSB) repair and checkpoint signaling through undefined interactions with ATM, MDC1, and Sae2/Ctp1/CtIP. Here, fission yeast and human Nbs1 structures defined by X-ray crystallography and small angle X-ray scattering (SAXS) reveal Nbs1 cardinal features: fused, extended, FHA-BRCT1-BRCT2 domains flexibly linked to C-terminal Mre11- and ATM-binding motifs. Genetic, biochemical, and structural analyses of an Nbs1-Ctp1 complex show Nbs1 recruits phosphorylated Ctp1 to DSBs via binding of the Nbs1 FHA domain to a Ctp1 pThr-Asp motif. Nbs1 structures further identify an extensive FHA-BRCT interface, a divalent MDC1-binding scaffold, an extended conformational switch, and the molecular consequences associated with cancer predisposing Nijmegen breakage syndrome mutations. Tethering of Ctp1 to a flexible Nbs1 arm suggests a mechanism for restricting DNA end processing and homologous recombination activities of Sae2/Ctp1/CtIP to the immediate vicinity of DSBs.

Williams RS, Dodson GE, Limbo O, Yamada Y, Williams JS, Guenther G, Classen S, Glover MJN, Iwasaki H, Russell P, Tainer JA. “Nbs1 Flexibly Tethers Ctp1 and Mre11-Rad50 to Coordinate DNA Double-Strand Break Processing and Repair” Cell, Volume 139, Issue 1, 87-99, 2 October 2009
link out
Wen Zhang and Jack Dunkle in the Cate lab have a nice report out in the August 21, 2009 issue of Science describing their latest crystal structures of the E. coli ribosome with and without tRNA mimcs. These new structure shed light on the rachet-like action of the intact ribosome as it interacts with tRNA in the A, P, and E sites.

Zhang_Dunkle_Cate_Science.jpegAbstract:
Protein biosynthesis on the ribosome requires repeated cycles of ratcheting, which couples rotation of the two ribosomal subunits with respect to each other, and swiveling of the head domain of the small subunit. However, the molecular basis for how the two ribosomal subunits rearrange contacts with each other during ratcheting while remaining stably associated is not known. Here, we describe x-ray crystal structures of the intact Escherichia coli ribosome, either in the apo-form (3.5 angstrom resolution) or with one (4.0 angstrom resolution) or two (4.0 angstrom resolution) anticodon stem-loop tRNA mimics bound, that reveal intermediate states of intersubunit rotation. In the structures, the interface between the small and large ribosomal subunits rearranges in discrete steps along the ratcheting pathway. Positioning of the head domain of the small subunit is controlled by interactions with the large subunit and with the tRNA bound in the peptidyl-tRNA site. The intermediates observed here provide insight into how tRNAs move into the hybrid state of binding that precedes the final steps of mRNA and tRNA translocation.

Zhang W, Dunkle JA, Cate JHD. "Structures of the Ribosome in Intermediate States of Ratcheting" Science 21 August 2009: Vol. 325. no. 5943, pp. 1014 - 1017.
link out

Yeah!

Come collect data on our newly upgraded ADSC Q315r area detector.

Here is the "proof"

q315r_lysozyme.png

New DOMO Sample Dewar Lid

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We've installed a sweet new blue anodized aluminum air dam on the pneumatic lid for the DOMO sample dewar (with color coordinated electric blue CPU fans). The air dam helps to draw off frozen ice crystals from the air above the liquid nitrogen when the dewar lid is open. This will hopefully prevent the ice from falling into the LN2 and contaminating it. If it doesn't work at least it looks cool. 211207_dewar.jpg

DOMO (Dynamic Offsite MX(Macromolecular Crystallography) Operator) mounted crystals remotely for the first time today. The user accessed the beamline via port 22 (i.e. ssh) from San Diego using NX Client and was able to successfully screen through 50 or so crystals. Although I could have monitored the shift from my office, from home, or from Tahiti, I thought it would be more prudent to remain close to the beamline in the unlikely event that intervention was needed…. Well I’m glad that I stuck around. Although DOMO performed well, there were a couple of times that I needed to step in a make things right. Overall, however, it was a very successful first run.

If you are interested in collecting crystallographic data from the comfort of your own lab (or Tahiti) I would encourage you to apply for time on the SIBYLS beamline. We have a small supply of sample cassettes and the necessary tools for loading the cassettes. A cassette kit can be sent to you, whereupon you load the cassette with your valuable samples, and thusly send it back to the beamline in time for your shift. It’s loads of fun!

X-Ray Emission Spectra

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K-level and L-level emission lines in KeV

No. Element Kα1       Kα2       Kβ1       Lα1       Lα2       Lβ1       Lβ2       Lγ1

3   Li      0.0543
4   Be      0.1085
5   B       0.1833
6   C       0.277
7   N       0.3924
8   O       0.5249
9   F       0.6768
10  Ne      0.8486    0.8486
11  Na      1.04098   1.04098   1.0711
12  Mg      1.25360   1.25360   1.3022
13  Al      1.48670   1.48627   1.55745
14  Si      1.73998   1.73938   1.83594
15  P       2.0137    2.0127    2.1391
16  S       2.30784   2.30664   2.46404
17  Cl      2.62239   2.62078   2.8156
18  Ar      2.95770   2.95563   3.1905
19  K       3.3138    3.3111    3.5896
20  Ca      3.69168   3.68809   4.0127    0.3413    0.3413    0.3449
21  Sc      4.0906    4.0861    4.4605    0.3954    0.3954    0.3996
22  Ti      4.51084   4.50486   4.93181   0.4522    0.4522    0.4584
23  V       4.95220   4.94464   5.42729   0.5113    0.5113    0.5192
24  Cr      5.41472   5.405509  5.94671   0.5728    0.5728    0.5828
25  Mn      5.89875   5.88765   6.49045   0.6374    0.6374    0.6488
26  Fe      6.40384   6.39084   7.05798   0.7050    0.7050    0.7185
27  Co      6.93032   6.91530   7.64943   0.7762    0.7762    0.7914
28  Ni      7.47815   7.46089   8.26466   0.8515    0.8515    0.8688
29  Cu      8.04778   8.02783   8.90529   0.9297    0.9297    0.9498
30  Zn      8.63886   8.61578   9.5720    1.0117    1.0117    1.0347
31  Ga      9.25174   9.22482   10.2642   1.09792   1.09792   1.1248
32  Ge      9.88642   9.85532   10.9821   1.18800   1.18800   1.2185
33  As      10.54372  10.50799  11.7262   1.2820    1.2820    1.3170
34  Se      11.2224   11.1814   12.4959   1.37910   1.37910   1.41923
35  Br      11.9242   11.8776   13.2914   1.48043   1.48043   1.52590
36  Kr      12.649    12.598    14.112    1.5860    1.5860    1.6366
37  Rb      13.3953   13.3358   14.9613   1.69413   1.69256   1.75217
38  Sr      14.1650   14.0979   15.8357   1.80656   1.80474   1.87172
39  Y       14.9584   14.8829   16.7378   1.92256   1.92047   1.99584
40  Zr      15.7751   15.6909   17.6678   2.04236   2.0399    2.1244    2.2194    2.3027
41  Nb      16.6151   16.5210   18.6225   2.16589   2.1630    2.2574    2.3670    2.4618
42  Mo      17.47934  17.3743   19.6083   2.29316   2.28985   2.39481   2.5183    2.6235
43  Tc      18.3671   18.2508   20.619    2.4240    -         2.5368    -         -
44  Ru      19.2792   19.1504   21.6568   2.55855   2.55431   2.68323   2.8360    2.9645
45  Rh      20.2161   20.0737   22.7236   2.69674   2.69205   2.83441   3.0013    3.1438
46  Pd      21.1771   21.0201   23.8187   2.83861   2.83325   2.99022   3.17179   3.3287
47  Ag      22.16292  21.9903   24.9424   2.98431   2.97821   3.15094   3.34781   3.51959
48  Cd      23.1736   22.9841   26.0955   3.13373   3.12691   3.31657   3.52812   3.71686
49  In      24.2097   24.0020   27.2759   3.28694   3.27929   3.48721   3.71381   3.92081
50  Sn      25.2713   25.0440   28.4860   3.44398   3.43542   3.66280   3.90486   4.13112
51  Sb      26.3591   26.1108   29.7256   3.60472   3.59532   3.84357   4.10078   4.34779
52  Te      27.4723   27.2017   30.9957   3.76933   3.7588    4.02958   4.3017    4.5709
53  I       28.6120   28.3172   32.2947   3.93765   3.92604   4.22072   4.5075    4.8009
54  Xe      29.779    29.458    33.624    4.1099    -         -         -         -
55  Cs      30.9728   30.6251   34.9869   4.2865    4.2722    4.6198    4.9359    5.2804
56  Ba      32.1936   31.8171   36.3782   4.46626   4.45090   4.82753   5.1565    5.5311
57  La      33.4418   33.0341   37.8010   4.65097   4.63423   5.0421    5.3835    5.7885
58  Ce      34.7197   34.2789   39.2573   4.8402    4.8230    5.2622    5.6134    6.052
59  Pr      36.0263   35.5502   40.7482   5.0337    5.0135    5.4889    5.850     6.3221
60  Nd      37.3610   36.8474   42.2713   5.2304    5.2077    5.7216    6.0894    6.6021
61  Pm      38.7247   38.1712   43.826    5.4325    5.4078    5.961     6.339     6.892
62  Sm      40.1181   39.5224   45.413    5.6361    5.6090    6.2051    6.586     7.178
63  Eu      41.5422   40.9019   47.0379   5.8457    5.8166    6.4564    6.8432    7.4803
64  Gd      42.9962   42.3089   48.697    6.0572    6.0250    6.7132    7.1028    7.7858
65  Tb      44.4816   43.7441   50.382    6.2728    6.2380    6.978     7.3667    8.102
66  Dy      45.9984   45.2078   52.119    6.4952    6.4577    7.2477    7.6357    8.4188
67  Ho      47.5467   46.6997   53.877    6.7198    6.6795    7.5253    7.911     8.747
68  Er      49.1277   48.2211   55.681    6.9487    6.9050    7.8109    8.1890    9.089
69  Tm      50.7416   49.7726   57.517    7.1799    7.1331    8.101     8.468     9.426
70  Yb      52.3889   51.3540   59.37     7.4156    7.3673    8.4018    8.7S88    9.7801
71  Lu      54.0698   52.9650   61.283    7.6555    7.6049    8.7090    9.0489    10.1434
72  Hf      55.7902   54.6114   63.234    7.8990    7.8446    9.0227    9.3473    10.5158
73  Ta      57.532    56.277    65.223    8.1461    8.0879    9.3431    9.6518    10.8952
74  W       59.31824  57.9817   67.2443   8.3976    8.3352    9.67235   9.9615    11.2859
75  Re      61.1403   59.7179   69.310    8.6525    8.5862    10.0100   10.2752   11.6854
76  Os      63.0005   61.4867   71.413    8.9117    8.8410    10.3553   10.5985   12.0953
77  Ir      64.8956   63.2867   73.5608   9.1751    9.0995    10.7083   10.9203   12.5126
78  Pt      66.832    65.112    75.748    9.4423    9.3618    11.0707   11.2505   12.9420
79  Au      68.8037   66.9895   77.984    9.7133    9.6280    11.4423   11.5847   13.3817
80  Hg      70.819    68.895    80.253    9.9888    9.8976    11.8226   11.9241   13.8301
81  Tl      72.8715   70.8319   82.576    10.2685   10.1728   12.2133   12.2715   14.2915
82  Pb      74.9694   72.8042   84.936    10.5515   10.4495   12.6137   12.6226   14.7644
83  Bi      77.1079   74.8148   87.343    10.8388   10.73091  13.0235   12.9799   15.2477
84  Po      79.290    76.862    89.80     11.1308   11.0158   13.447    13.3404   15.744
8S  At      81.52     78.95     92.30     11.4268   11.3048   13.876    -         16.251
86  Rn      83.78     81.07     94.87     11.7270   11.5979   14.316    -         16.770
87  Fr      86.10     83.23     97.47     12.0313   11.8950   14.770    14.45     17.303
88  Ra      88.47     85.43     100.13    12.3397   12.1962   15.2358   14.8414   17.849
89  Ac      90.884    87.67     102.85    12.6520   12.5008   15.713    -         18.408
90  Th      93.350    89.953    105.609   12.9687   12.8096   16.2022   15.6237   18.9825
91  Pa      95.868    92.287    108.427   13.2907   13.1222   16.702    16.024    19.568
92  U       98.439    94.665    111.300   13.6147   13.4388   17.2200   16.4283   20.1671
93  Np      -         -         -         13.9441   13.7597   17.7502   16.8400   20.7848
94  Pu      -         -         -         14.2786   14.0842   18.2937   17.2553   21.4173
95  Am      -         -         -         14.6172   14.4119   18.8520   17.6765   22.0652

Values are from J. A. Bearden, “X-Ray Wavelengths”, Review of Modern Physics, (January 1967) pp. 86-99, unless otherwise noted.

Eight easy steps to connect to the SIBYLS NX server through the beamline firewall. These instructions will work for OS X and Linux. We've also compiled more detailed instructions when connecting from a Windows PC.

1. Download and Install NoMachine NX Client.

2. Launch the NX Client and create a new connection.

name it whatever you want
Host: kona.als.lbl.gov
Protocol: SSH
Port: 22

3. Under the Advanced Settings check the "Use the NoMachine login" box.

4. Use your SIBYLS computer account username and password. When you connect for the first time I believe you will be prompted to accept the server key. Just click "yes".

5. you will then need to create a new desktop session. Please select Gnome Desktop. We don't have any of the other window managers installed.

6. You are now connected to kona and should have a desktop available to you. You may want to make it fullscreen and set the 1:1 pixel option to make the best use of your monitor.

Q315 Temperature Control

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The detector can be brought up to essentially room temperature (in order to gracefully shut it down or do other work on it) or brought down to -40°C (to minimize detector noise for data collection) using the “Quantum Console” program on the detector computers.

This figure shows a fairly typical screen image on the detector computers.

In the image shown, the “REMOTE Detector OP” program is already running (as a DOS window). If this program is not running, it needs to be run before the Quantum Console can control the detector modules. The shortcut to the program is highlighted by one of the white circles.

Once the “REMOTE Detector OP” program, hereafter the detector program, is running on all nine modules, you can control the detector temperature by running the Quantum Console program on any one of the detector computers. The shortcut for this program is highlighted by the other white circle.

When the Quantum Console starts, it will open a window that looks something like this:

Before you can do anything else, you need to click on “Connect to Detector Processes.” This will create a row of status reports and allow you to click on “ENABLE Temperature Control”, resulting in a window something like this one:

This window actually shows a temperature-change operation that is already under way, but all the essential parts are visible.

If all is as it should be, setting the temperature is fairly simple. To cool the detector down for operation, click “Ramp to Cold Operating Temp”. To warm it up, click on “Warm up Detector to +10°C”. Either one will gradually bring the detector to the desired temperature. Shifting by the whole range from +10°C to -45°C, in either direction, generally takes about an hour.

Unfortunately, it is occasionally necessary to restart the ADSC detector along with the associated software. This will summarize how that is done. We will assume that everything is up and running at the beginning of the process; starting when some component or other is down is essentially the same.

We’ll assume that this is only a short interruption and that we don’t have to worry about the detector vacuum.

Begin by bringing the detector to room temperature (or +10C) as described in “Detector Temperature Settings.”

Once the detector is warmed up, it can be shut down at the power switches —- it is not necessary to shut down the detector processes or other software first.

Turn the detector power switches (the green switches highlighted by the arrow) off from top to bottom. The main power switches should be turned on starting with the bottom power module, then the middle module, then the top module. The order does matter.

If you don’t have the “REMOTE Detector OP” processes running yet, this is the time to start them. Double click on the “REMOTE Detector OP” shortcut, and you should see a DOS window appear:

Even if you already had these processes running when you restarted the detector, they still must be sent a reset signal. We generally do this from a script. The script makes up part of /programs/beamline/nuke, so it can be found there, but for completeness, here is the one we’ve been using:

foreach module ( detector0 detector1 detector2 detector3 detector4 detector5 detector6 detector7 detector8 )
    # send the reset signal
    echo -n "$module restart "
    echo "restart" | sock_exchange.tcl $module 8038 1
    echo ""
end

Entering that script at a shell prompt at any of the BL12.3.1 Linux consoles should reset the whole group of detectors. (Since the BLU-ICE/DCSS control programs run on dataserver, that is a good place to run the script.) This reset signal will cause lots of activity on the “REMOTE Detector OP” windows:

Beamline Diagram

Focus Beam at Beamstop with Experimental Table Between PX and SAXS

Check Helium tank outside of hutch to make sure it is full and that it is flowing into the shutter box. It is important to purge all air from the shutterbox as the ion-guage needs to report a consistent value.

Turn Helium on as early as possible to assure shutterbox is purged

In a terminal window turn off the feedback with the following command:


feedback.com off

Switch KVM to the Beamline computer, and launch "Shortcut to BL Control Main".

Click the white arrow in upper left of main window. This will open the "Beamline 12.3.1 Beamline Control System" window.

Open bothe the Motor Debugger and Motor Monitor modules from the "Motors" pulldown menu.

Turn on autoscaling under the "Amplifiers" pulldown main menu. (why?)

Set M2 Bend Up to 244000, and click move button.

Set M2 Bend Down to 267000, and click move button.

Change "Mono eV" to 10000.

Remove the safety pin and use the hand crank to move the table to the mid point. There is a piece of red tape marked in pen "YAG" indicating the proper midpoint position of the table.

Attach the BNC cable to the camera that monitors the YAG prism, and focus the camera (this step will hopefully be unnecessary once a more permanent camera position is established.

Close the hutch.

Open the main shutter. You should see the direct beam hitting the YAG prism at this point.

Select "tune rocking curve" and click either the step ⬆ or the step ⬇ button once to initialize the optimization procedure. (this automagically adjusts Theta2)

Select "M2 Tilt" and click the home button to reset all values to 0.000

Move M2 Tilt to 12000.

Some PX users will have adjusted the Slits1 to make a very tight beam so they should checked and backed off if necessary. Aperture Line 1 and Aperture Line 11 values should be decreased several unit values.

If you lose the beam jog M2 Tilt in 100 unit increments (this should move the beam up and down on the video monitor).

Select "Chi2" (value should be ~0.492) jog Chi2 in 0.01 increments. (this should move the beam left and right on the video monitor). Because Chi2 is adjusting the focus of the beam changes to this value will drastically alter the shape of the beam.

Sometimes the table will need to be moved slightly in order to position the beam in the middle of the YAG. Additionally the shutter control cable may sometimes get in the way so it must be unplugged from the shutterbox. Turn off power on shutter control box and unplug cable.

Close hutch and turn off hutch light.

Open main shutter and make sure video monitor is turned on.

Optimize the shape and size of the beam. You want it as round and small as possible. Make small adjustments to both Chi2 and M2 Tilt.

Move Experimental Table to SAXS Position

Move the table all the way into SAXS mode using the hand crank. There is a digital dial attached to the air table's sub-frame. Crank the table until this value reads zero.

Re-attach the shutter control cable to the shutter box and turn on the power to the shutter control box. Press the small red button on the shutter control box to really turn it back on.

Close hutch and open main shutter.

Optimize Slits 1, Slits 2, and Slits3 - itertatively

Make sure that the video signal going to the beamline computer is displaying the Beam Position Monitor (BPM) video-feed from the camera that points into the shutter box.

Turn on feedback with the following command:

feedback.com on

The point here is to move slits1 (Aperture guys) and slits2 (SAXS aperture guys) and slits3 (Guard Slits guys) back in as far as possible without actually clipping the beam.

The beam on the back of the shutter may be a bit rough on the bottom edge as a result of nicking slits2 and may look like this:

Jog M2 Tilt to move the whole beam slightly up.

Make sure the High Voltage control unit that feeds the ion guage in the shutterbox has not been tripped. If it has been tripped then reset and increase voltage to as close to 300V as possible.

Close all four slits1 blades as far as possible without clipping beam.

  • Aperture Line 1 moves in from the right
  • Aperture Line 11 moves in from the left
  • Aperture Upper moves in from the top... duh
  • Aperture Lower moves in from the bottom... duh

Close all four slits2 blades as far as possible without clipping beam.

  • SAXS Aperture Line 1 moves in from the right
  • SAXS Aperture Line 11 moves in from the left
  • SAXS Aperture Upper moves in from the bottom... huh?
  • SAXS Aperture Lower moves in from the top... huh?

Insert all filters into direct beam and take a 1sec shot on the MAR CCD.

Close all four slits3 blades as far as possible without clipping beam.

  • Guard Slits 1 more + values to close blade down. (Left side)
  • Guard Slits 11 more - values to close blade down. (Right side)
  • Guard Slits Upper more + values to close blade down.
  • Guard Slits Lower more - values to close blade down.

Reduce Reflections from Slits3 and adjust beamstop

Take a 1 sec shot on MAR CCD. It will look something like this:

Back off the Guard Slits Upper and Guard Slits Lower until the vertical streaking is eliminated. (streaking toward the top of the screen is caused by Guard Slits Lower being too far in, and vice-a versa for streaking downwards)

Back off the Guard Slits 1 and Guard Slits 11 until the horizontal streaking is eliminated. (this is usually less of a problem, but again streaking to the left is caused by x-rays reflecting off of Guard Slits 11, and vice-a-versa for streaking to the right)

Adjust Endstop y to move the beamstop up and down.

Adjust Endstop x to move the beamstop left and right.

Center the beamstop by observing a line integration tool drawn though the beamstop. The idea is to get a symmetrical background scatter aboce and below the beamstop shadow.

Define Beam for Users

Enter hutch. Manually open the experimental shutter. Insert CCD shield. Insert sample cell with fluorescent paper.

Close hutch. Open main shutter and define the bounding box for the beam on the video monitor.

It may be necessary to move the sample up or down (Sample x and Sample y) so that the beam enters the sample cell in the center.

Enter hutch. Close experimental shutter. Remove CCD shield.

You are now ready to CRUSH!!!!!

A new review on macromolecular SAXS has been published in the Quarterly Reviews in Biophysics by Putnam, C.D., Hammel, M., Hura, G.L., and Tainer, J.A.

“This six part review addresses both theoretical and practical concepts, concerns and considerations for using these techniques in conjunction with computational methods to productively combine solution scattering data with high-resolution structures.”

The review provides an extensive and up-to-date review on the application of small angle X-ray scattering is available for download.

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