We report the low temperature carbon monoxide recombination kinetics after photolysis and the temperature dependence of the visible absorption spectra of the isolated alpha SH-CO and beta SH-CO subunits from human hemoglobin A in ethylene glycol/water and in glycerol/water mixtures. Kinetic measurements on sperm whale (Physeter catodon) myoglobin and previously published optical spectroscopy data on the latter protein and on human hemoglobin A, in both solvents, (Cordone, L., A. Cupane, M. Leone, E. Vitrano, and D. Bulone. 1988. J. Mol. Biol. 199:312-218) are taken as reference. Low temperature flash photolysis data are analyzed within the multiple substates model proposed by Frauenfelder and co-workers (Austin, R. H., K. W. Beeson, L. Eisenstein, H. Frauenfelder, and I. C. Gunsalus. 1975. Biochemistry. 14:5355-5373). Within this model a distribution of activation enthalpies for ligand binding accounts for the structural heterogeneity of the protein, while the preexponential factor, containing also the entropic contribution to the free energy of the process, is considered to be constant for all conformational substates. Optical spectra are deconvoluted in gaussian components and the temperature dependence of the moments of the resulting bands is analyzed, within the harmonic Frank-Condon approximation, to obtain information on the stereodynamic properties of the heme pocket. The kinetic and spectral parameters thus obtained are found to be protein dependent also with respect to their sensitivity to changes in the composition of the external medium. A close correlation between the kinetic and spectral features is observed for the proteins examined under all experimental conditions studied. The results reported are discussed in terms of differences in the heme pocket structure and in the conformational heterogeneity among the various proteins, as related to their different capability to accommodate constraints imposed by the external medium.

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Due to their high numerical efficiency, homogenization models are often employed in the analysis of corrugated laminates. They are usually derived assuming periodic behavior in the corrugated direction and generalized plane strain in the out-of-plane direction, which corresponds to the assumption of infinite dimensions of the structure. As a consequence, any influences of edge effects are not mapped, although they can have a significant impact on the mechanical behavior of a given structure. The objective of this manuscript is to investigate the influence of boundary conditions - a combination of free-edges and clamping - on the structural stiffness of corrugated laminates. A total of six load cases are investigated which correspond to the line loads considered in the classical theory of laminated plates. The results of this parameter study allow the identification of several critical loading situations, where free edges can significantly alter structural stiffness. The given investigations hence contribute to the investigation of the validity range of homogenization models.

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