PHYCOBILIPROTEINS: COMPARISON OF SOLUTION AND SINGLE CRYSTAL FLUORESCENCE FOR C-PHYCOCYANIN AND B-PHYCOERYTHRIN*

Abstract— Trimeric and hexameric solution forms of C-phycocyanin (CPC) from the cyanophyte Agme-nellum quadruplicatum have been isolated and their spectral properties compared to those obtained from single crystals. Although the absorbance peak of a suspension of small C-phycocyanin crystals is red-shifted only 7 nm relative to the solution forms, the single crystal fluorescence is red-shifted 60 nm relative to the solution forms. The crystal fluorescence spectrum exhibits a single peak at LD_max= 708 nm when excited at 514.5 or 530.9 nm and two peaks (LD_max= 661 and 708 nm) when excitation occurs at 568.2 nm. Fluorescence depolarization measurements indicate that extensive energy transfer could occur for both solution and crystal forms with the latter being dependent upon the relative orientation of the crystal with respect to the excitation dipole. Similar results were obtained with B-phycoerythrin (BPE) from the red alga Porphyridium cruentum where the single crystal fluorescence is red-shifted =50nm relative to the solution spectra with two peaks (LD_max= 583 and 617 nm) observed whose relative intensities are dependent on the excitation wavelength (LD_max– 514.5 and 530.9 nm). Single crystal fluorescent lifetimes exhibited considerable shortening relative to that observed for the solution forms. The implications of these results are discussed with respect to the possible relationships of the crystalline structures to the assembly forms present within phycobilisomes.     

Reaction of γ-picoline N-oxide with ketenimines in the presence of organic acids: Preparation of α-acyloxyamides

A synthesis of a-acyloxyamides is described which utilizes the reaction of 7-picoline N-oxide and various organic acids with diphenylketene N-p-tolylimine.     

New combining rules for rare gas van der waals parameters

New combining rules are proposed for the well depth, ?, and interaction distance, σ, describing nonbonded interatomic forces for rare gas pair interactions. Concepts underlying current combining rules applied in simulations of macromolecular and polymer systems are shown to be incompatible with experimental data on the rare gases. The current combining rules are compared with the new results using the experimental data. Mathematical properties of combining rules are considered, and it is shown how to reduce combining rule formulas from a two-parameter to a single-parameter problem. It is also shown how to graphically analyze combining rules against experimental data. We demonstrate using this analysis technique that the rare gas potentials do not obey a single combining rule for the ? parameter but do follow a single combining rule for the σ parameter. Finally, we demonstrate that a combining rule using both ? and ω can be used to predict the ? parameters for the mixed rare gas pairs. © John Wiley & Sons, Inc.     

Photolysis of (η5-C5H5)2V(CH3)2: II . Photo-induced formation of ethane

Photolysis of (η⁵-C₅H₅)₂V(CH₃)₂ results in the formation of methane and ethane. The percentage of ethane detected in the evolved gas can vary from a trace to 70%. The percentage of ethane formed is dependent on the solvent, the concentration of (η⁵-C₅H₅)₂V(CH₃)₂, time and temperature. The results of oxidation and reduction reactions involving (η⁵-C₅H₅)₂V(CH₃)₂ are also presented.     

Preparation,properties and crystal structure of 1,2,5,6-tetrathiacyclooctane : The elusive mesocyclic bis-disulfide

The synthesis of the eight-membered ring containing two disulfides, 1,2,5,6-tetrathiacyclooctane, is described. It is characterized by x-ray crystallography as well as by mass, IR, Raman, ¹H-NMR und UV spectroscopy     

On J. Bolyai's parallel construction

Given a model of Hilbert's incidence, order and congruence axioms (an H-plane) in which the Line-Circle Principle and the hypothesis of the acute angle hold, J. Bolyai's parallel construction is shown to yield the two parallels through the given point that have a common perpendicular at infinity with the given line through the ideal points at which they meet the given line; these need not be asymptotic parallels, for the plane need not be hyperbolic. Two new characterizations of hyperbolic planes are given, based on W. Pejas' classification of H-planes. The role of Archimedes' axiom is clarified.     

Discrete velocity models with small data

Summary It is shown that all discrete velocity models conserving mass, momentum and energy and without self-interactions have global, uniformly bounded solutions for small enough initial data with compact support. This is interesting because of a recent example with small data inL ¹ L whose solution is not bounded, and shows the unboundedness is due to mass being fed in from infinity.

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Sommario Si dimostra che tutti i modelli con velocità discretizzate che conservano la massa, la quantità di moto e l'energia e senza autointerazioni hanno soluzioni globali, uniformemente limitate per dati iniziali a supporto compatto e abbastanza piccoli. Questo è interessante a causa di un esempio recente con dati piccoli inL ¹ L la cui soluzione non è limitata e mostra che l'illimitatezza è dovuta ad un flusso di massa dall'infinito.

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Research supported by the Natural Science and Engineering Research Council Canada under Grant No. A8560.     

Theoretical study of relaxation at the (110) Ge-GaAs interface

A simple relaxation of the Ge-GaAs (110) interface is studied theoretically using self-consistent pseudopotentials. The relaxation is one in which the distance between the Ge and GaAs atomic planes at the interface is increased by 20%. Band edge discontinuities are found to be insensitive to this type of relaxation in spite of large distortions of the electronic charge density.     

On Dirichlet series satisfying Riemann's functional equation

Summary According to convention, Hamburger's theorem (1921) says-roughly-that Riemann's (s) is uniquely determined by its functional equation. In 1944 Hecke pointed out that there are two distinct versions of Hamburger's theorem. Hecke's remark has led me, in examining just how rough the convention is, to prove that, with a weakening of certain auxiliary conditions, there are infinitely many linearly independent solutions of Riemann's functional equation (Theorem 1). In Theorem 1, as in Hamburger's theorem, the weight parameter is 1/2. In Theorem 2 we obtain stronger results when this parameter is 2: a Mittag-Leffler theorem for Dirichlet series with functional equations.Oblatum 23-XII-1992 & 9-IX-1993Research supported in part by NSA/MSP Grant MDA 90-H-4025 To the memory of Martin Eichler