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L J Weissman

Publications and source records attributed to L J Weissman.

3 recordsLinked to original sources
PubMed1990

Fractal descriptions for spatial statistics.

Measures of spatial statistics have been available for estimating means, calculating or assessing differences, estimating nearest neighbor distances, and such, but have not provided a general approach to describing variances. Because measures of heterogeneity depend upon choosing a particular element size in the domain, estimates of apparent heterogeneity are larger with high-resolution observations than with low-resolution data. Many descriptors might be used to describe the relationships between apparent heterogeneity and the size of the observed spatial elements, but we have found that fractal relationships provide concise and precise descriptions of many types of data over large ranges of element sizes. Perhaps more importantly, the fractal approaches give additional insight, such as measures of spatial correlation, and often suggest ways of approaching the underlying basis of the heterogeneity.

Animals↗
PubMedDate not supplied

Crystal structure of calmodulin.

The crystal structure of calmodulin has been determined to 3.6 A resolution. At this resolution the polypeptide chain can be traced. Some of the side chains have tentatively been identified. Refinement of the structure with x-ray diffraction data measured to 1.65 A resolution is continuing. As reported by Babu et al. calmodulin is about 65 A long and 30 A in diameter. Homolog domains 1 and 2 are related by a local twofold axis, as in parvalbumin and in troponin C, and form one end of the molecule. Domains 3 and 4 form the other end. The second alpha-helix of domain 2 and a short interdomain region are continuous with the first helix of domain 3, thereby forming a single helix from residues 67-93. The central region, residues 75-84, of this long helix forms a handle connecting the two pairs of homolog domains. Exclusive of the residues, 75-84, in the handle the closet approach of side chains of pair 1, 2 to pair 3, 4 is 12 A. The spatial relationship of pair 1, 2 to pair 3, 4 is similar in calmodulin to the relationship of the corresponding pairs in troponin C. However, in troponin C there are three additional residues in the handle region of the long alpha-helix and the two pairs are about 5.0 A further apart. On the surface of pair 1, 2 in calmodulin there is one extended region with many hydrophobic side chains from both domain 1 and domain 2. This hydrophobic patch is bounded by two distinct clusters of anionic side chains, one from the beginning of the first helix of domain 1 and on the other side of the hydrophobic surface one from the beginning of the first helix of domain 2. Homologously, the hydrophobic patch on the surface of pair 3, 4 is bounded by two clusters of aspartate and glutamate residues. Either or both of these hydrophobic surfaces may be sites to which calmodulin target proteins bind.

Amino Acid Sequence↗