Caspar

Wen X, Meyer R B and Caspar OLD 1989 Observation of smectic-A ordering in a solution of rigid-rod-like particles Rhys. Rev. Lett. 63 2760-3... 

Can any number of identical subunits be accommodated in the asymmetric unit while preserving specificity of interactions within an icosahedral arrangement This question was answered by Don Caspar then at Children s Hospital, Boston, and Aaron Klug in Cambridge, England, who showed in a classical paper in 1962 that only certain multiples (1, 3, 4, 7...) of 60 subunits are likely to occur. They called these multiples triangulation numbers, T. Icosahedral virus structures are frequently referred to in terms of their trian-gulation numbers a T = 3 virus structure therefore implies that the number of subunits in the icosahedral shell is 3 x 60 = 180. 

The S domains form the viral shell by tight interactions in a manner predicted by the Caspar and Klug theory and shown in Figure 16.8. The P domains interact pairwise across the twofold axes and form protrusions on the surface. There are 30 twofold axes with icosahedral symmetry that relate the P domains of C subunits (green) and in addition 60 pseudotwofold axes relating the A (red) and B (blue) subunits (Figure 16.9). By this arrangement the 180 P domains form 90 dimeric protrusions. 

X-ray studies at 22.5 A resolution of murine polyomavlrus by 1. Rayment and D.L.D. Caspar at Brandeis University confirmed the presence of these 72 capsomers at the expected positions, but even at low resolution the pentagonal shape of all 72 capsomers was evident (Figure 16.22). They concluded that each capsomer must be a pentameric assembly of the major viral subunit, known as viral protein 1 (VPl). Each of the 60 icosahedral asymmetric units contains 6 VPl subunits, not 7, and the complete shell contains 360 VPl subunits. The 12 VPl pentamers centered on icosahedral fivefold axes are identically related to their five neighbors, but the 60 pentamers centered on pseudosixfold positions "see" each of their 6 neighbors quite differently (Figure 16.23). How can such diversity of interaction be incorporated into the bonding properties of just one type of protein subunit, without compromising specificity and accuracy of assembly ... 

Caspar, D.L.D., Klug, A. Physical principles in the construction of regular viruses. Cold Spring Harbor Symp. Quant. Biol 27 1-24, 1962. 

S. S. H. Naqvi, S. M. Caspar, K. C. Hickman, and J. R, McNeil. A Simple Technique for Linewidth Measurement of Gratings on Photomasks. Proc. SPIE. 1261, 495, 1990. K.P. Bishop, S.M. Caspar, L.M. Milner, S.S.H. Naqvi, and J.R, McNeil, rasterization using Scatterometry. Proc. SPIE. 1545, 64, 1991. These papers discusses a simple application of scattering from surhices that are intentionally patterned. 

K. C. Hickman, S. M. Caspar, S. S. H. Naqvi, K. P. Bishop, J. R, McNeil, G. D. Tipton, B. R, Stallard, and B. L. Draper. Use of Diffraction From Latent Images to Improve Lithogrophy Control. Presented at the SPIE Technical Conference 1464 Symposium on I.C. Metrology, Inspection, and Process Control, San Jose, CA, 1991, Proc. SPIE. 1464, pp. 245-257, 1991. Another application is presented of scattering characterization and modeling from periodic structures for process control. 

Ksenofontov V, Caspar AB, Giitlich P (2004) Pressure Effect Studies on Spin Crossover and Valence Tautomeric Systems. 235 23-64 Ksenofontov V, see Real JA (2004) 233 167-193... 

There is a discussion of these ideas in relation to the theology of Caspar Schwenckfeld in Seguenny, Les Spirituels (2000), 554 ff. 

Skaar EP, AH Caspar, O Schneewind (2004) IsdG and Isdl, heme-degrading enzymes in the cytoplasm of Staphylococcus aureus. J Biol Chem 279 436-443. 

Pirrone N, Hedgecock 1, Forlano L. 2000. The role of the ambient aerosol in the atmospheric processing of semi-volatile contaminants a parameterised numerical model (CASPAR). J Geophys Res 105(D8) 9773-9790. 

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