IV Structural Refinement and Protein Dynamics. 
The major impediment to an accurate simulation 
of diffraction data based on macromolecular mod- 
els from crystallography comes in the description of 
dynamic properties. Work supported in part by the 
National Science Foundation is directed at improv- 
ing descriptions of atomic mobility and thereby ad- 
vancing methods for structural refinement. Such 
improvements not only strengthen the reliability of 
atomic coordinates, but they also characterize sig- 
nificant dynamic features. Atomic mobility parame- 
ters from well-refined structures have been corre- 
lated with biochemical properties in several 
instances. The extension of crystallographic refine- 
ment methods to two-dimensional nuclear mag- 
netic resonance (NMR) structures is also being ex- 
amined. 
V The Phase Problem and Anomalous Diffraction. 
Diffraction experiments record only the ampli- 
tudes for diffracted waves, but both amplitudes and 
phases are required for a reconstruction of molecu- 
lar images. The evaluation of these phases presents 
the major conceptual difficulty in crystallography. 
Recent theoretical and practical advances in the 
analysis of multiwavelength anomalous diffraction 
(MAD) data have borne fruit in a number of appli- 
cations during the past year. In addition to reports 
published on earlier applications to lamprey hemo- 
globin, a bacterial ferredoxin, and streptavidin, new 
results have also been obtained. These studies have 
emphasized selenomethionyl proteins and bromi- 
nated nucleic acids as general phasing vehicles. The 
structures of selenomethionyl interleukin-la (with 
PUBLICATIONS 
Drs. Marcos Hatada and Brad Graves) and of the 
complex of chromomycin with d[TU^'"GGCCAA] 
have both been determined from data measured at 
the Photon Factory in Japan. Analyses of data on 
selenomethionyl thioredoxin and on selenome- 
thionyl ribonuclease H are also proceeding satisfac- 
torily. Finally, comprehensive measurements have 
been made for the MAD data associated with cop- 
per centers in the octopus hemocyanin fragment. 
Several advances in the theoretical and computa- 
tional analysis MAD data have been generated in 
the course of these applications. This work is sup- 
ported in part by the National Institutes of Health. 
VI. Hughes Synchrotron Resource. 
X-ray beam lines for use by HHMI investigators 
are in the late stages of construction at the National 
Synchrotron Light Source at Brookhaven National 
Laboratory. This resource features three beam lines: 
one with special capabilities for MAD experiments, 
another dedicated to Laue experiments and posi- 
tion monitoring, and a third for routinely rapid ro- 
tation photography and precession characteriza- 
tion. Evacuated beam tubes have been installed for 
all lines, and "first light" experiments have been 
conducted. Experimental hutches equipped for 
BL-2 biosafety containment have been installed on 
the MAD and rotation lines. Imaging phosphor 
reader systems have been obtained for efficient 
x-ray detection, and a facility to house this equip- 
ment is under construction. 
Dr. Hendrickson is also Professor of Biochemistry 
and Molecular Biophysics at Columbia University 
College of Physicians and Surgeons. 
Articles 
Bourne, PE. 1989. UNDC in a VMS world. DEC Professional 8(6): 106-1 13. 
Bourne, PE. 1989. File handling: UNIX versus VMS. DEC Professional 8(7):118-124. 
Bourne, PE. 1989. Roundtable: UNIX or VMS. DEC Professional 8(8):58-66. 
Bourne, PE., and Hendrickson, WA. 1988. Selecting a processor for computations in molecular biophysics. 
Comput Biol Med 18:341-349. 
Hendrickson, WA. 1989. Crystallographic citations. Science 242:347-348. 
Hendrickson, WA. , Pahler, A., Smith, J. L, Satow, Y, Merritt, E.A., and Phizackerley, R.P 1989. Crystal structure 
of core streptavidin determined from multiwavelength anomalous diffraction of synchrotron radiation. 
Proc Natl Acad Sci USA 86:2190-2194. 
Hendrickson, WA., Smith, J. L., Phizackerley, R.P, and Merritt, E.A. 1988. Crystallographic structure analysis of 
lamprey hemoglobin from anomalous dispersion of synchrotron radiation. Proteins 4:77-88. 
Continued 
586 
