Molecular Requirement of Chlorosomal Chlorophylls. Self-Organization of a Chlorophyll Derivative Possessing a Hydroxyl Group at Ring II

Aggregation of zinc 7¹-hydroxyl-13²-demethoxycarbonyl-pheophytin a (Zn-7¹-OH-Chl) was examined in relation to the structure and function of the self-aggregates of 3¹-OH-type chlorophylls (Chi) in chlorosomes of green photosynthetic bacteria. The Zn-7¹-OH-Chl aggregates yielded a Q_y absorption band at 712 nm with a 1.2-fold larger width (full width at half maximum, 500 cm⁻¹) than the monomer's (420 cm⁻¹). Infrared and NMR spectroscopies revealed that each molecule in the aggregate links together with simultaneous coordination (C7¹-OH…Zn) and hydrogen bonding (C7¹-OH … O=C13¹). A nonlinear alignment of the constituent molecules in the oligomeric structure was assumed. Despite the similar molecular linkages, linearly aligned Q_y, moments in the Zn-3¹-OH-Chl aggregate gave a chlorosome-like broader, more redshifted Q_y band (740 nm; 670 cm⁻¹, 2.1-fold larger than the monomer's). Because it is advantageous for efficient light harvesting and energy transfer to have several Q_y, spectral components, spread over a wide spectral range, that can act as the energy gradient, it is concluded that not only the intermolecular linkages but the linear locations of OH, C=0 and Mg in the molecule are crucial for photosynthetic antenna of the self-assembled chiorosomal Chl.     

Radioactivation analysis of hair a means of biological monitoring of the environment

With the aim of indicating environmental pollution effects by heavy metals on humans using hair, nondestructive activation analysis was applied to 382 normal Japanese hair samples (background level). Elemental contents of hair could be determined for Ag, Al, As, Br, Ca, Cd, Cl, Co, Cr, Cu, Fe, Hg, I, K, La, Mg, Mn, Na, S, Sb, Sc, Se, Sm, Ti, V and Zn. As these elements in hair have wide concentration ranges, the differences in concentrations distribution between groups (sex, age, permanent treatment and regional difference) are discussed. A method for hair sampling is presented.     

DISTRIBUTION OF ENZYMES INVOLVED IN NUCLEOTIDE METABOLISM IN THE DISK AND OTHER ROD MEMBRANES

Abstract— Intact disks and inverted disks were prepared from bovine retinal rods and the distribution in the disk membrane of such enzymes as guanyl cyclase, cyclic nucleotide phosphodiesterase, GTP binding protein (GTPase), 5'-nucleotidase and rhodopsin kinase was investigated. Guanyl cyclase was not detected in the disk; the enzyme activity was high in a membranous fraction containing the cilium or axoneme and the rod outer segment plasma membrane. Cyclic nucleotide phosphodiesterase, GTP binding protein (GTPase) and rhodopsin kinase were associated on the external surface of disk in the presence of 2 m M Mg²⁺. The enzymes dissociated from the membrane when Mg²⁺ was depleted. Thus, magnesium ion seems to regulate the state of these enzymes in the outer segment. 5'-Nucleotidase activity was low in intact disks but was significantly enhanced after inversion of the disk. The catalytic site of the enzyme, therefore, must be located on the internal (intradiscal) surface. Since the disks are known to be formed by invagination of the plasma membrane, 5'-nucleotidase, by inference, would have its catalytic site exposed on the external surface of the plasma membrane. Preliminary experiments showed that the capability of light-activated rhodopsin to activate cyclic nucleotide phosphodiesterase was inhibited by phosphorylation of the pigment. This supports the idea that rhodopsin kinase, cyclic nucleotide phosphodiesterase and GTPase exist as a functional complex on rod membranes.     

Enhanced microfiltration of γ-globulin solution upon treatment of NaCl addition and/or DNase digestion

Microfiltration of a γ-globulin solution has been investigated through the virus removal membranes having different pore sizes (i.e. r=15, 35 and 75 nm) and a dialysis membrane (r=3.4 nm), which were all made of the same regenerated cellulose material. The addition of NaCl in the γ-globulin feed solution was effective to enhance the flux and transmission through the membranes having a pore size ranging from 15 to 75 nm. DNase treatment of a γ-globulin solution with Micrococcal nuclease enhanced the flux and transmission of γ-globulin through the membranes either with or without NaCl. The membranes having a pore size of 35 nm showed dramatically enhanced flux in the microfiltration of a γ-globulin solution containing NaCl and/or being treated with Micrococcal nuclease. This can be explained as a DNase treatment and NaCl addition in the protein solution dissociate protein aggregates of DNA–γ-globulin complex, which plugs the pores in the microfiltration membranes.     

Metabolites of microorganisms. 144th communication. The crystal and molecular structure of 3-hydroxy-4-methylproline

A new amino acid isolated from the acid hydrolysate of the antibiotic Echinocandin B is shown by X-ray analysis to be 2,3–trans-3,4-cis-3-hydroxy-4-methylproline. The crystals are orthorhombic, a = 5.633 Å, b = 8.760 Å, c = 14.314 Å, Z = 4, space group P2₁2₁2₁. The structure was determined by direct methods and refined by least-squares analysis to a final R value of 0.032 for 532 reflections. The molecule exists as a zwitterion forming one O? H…O and two N? H…O hydrogen bonds.     

Angular dependence of screen speckle and fiber speckle of coupled output of nine high-power blue laser diodes through a multi-mode fiber

Angular dependence of speckle contrast of speckle pattern projected out of a multi-mode fiber connected to a high-power blue laser module is investigated. The laser module has nine high-power InGaN/GaN blue laser diodes arranged in a three-by-three array. Each of the arrayed laser diodes have slightly different incident angle to the fiber. We have successfully extracted the fine screen speckle pattern from the projected pattern mixed up with the coarse fiber speckle pattern by processing the measured data. It is found that the speckle contrast of the both screen and fiber speckles are larger around the center area where the guided-light component closest to the paraxial direction is projected. This is because the output of the center laser in the array is likely to couple into the paraxial mode more than the rest. Speckle contrast behaviors when applying the speckle reduction methods, fiber vibration, diffuser, and spinning diffuser are also investigated.     

PEG-detachable polyplex micelles based on disulfide-linked block catiomers as bioresponsive nonviral gene vectors

PEG-based polyplex micelles, which can detach the surrounding PEG chains responsive to the intracellular reducing environment, were developed as nonviral gene vectors. A novel block catiomer, PEG-SS-P[Asp(DET)], was designed as follows: (i) insertion of biocleavable disulfide linkage between PEG and polycation segment to trigger PEG detachment and (ii) a cationic segment based on poly(aspartamide) with a flanking N-(2-aminoethyl)-2-aminoethyl group, P[Asp(DET)], in which the Asp(DET) unit acts as a buffering moiety inducing endosomal escape with minimal cytotoxicity. The polyplex micelles from PEG-SS-P[Asp(DET)] and plasmid DNA (pDNA) stably dispersed in an aqueous medium with a narrowly distributed size range of approximately 80 nm due to the formation of hydrophilic PEG palisades while undergoing aggregation by the addition of 10 mM dithiothreitol (DTT) at the stoichiometric charge ratio, indicating the PEG detachment from the micelles through the disulfide cleavage. The PEG-SS-P[Asp(DET)] micelles showed both a 1-3 orders of magnitude higher gene transfection efficiency and a more rapid onset of gene expression than PEG-P[Asp(DET)] micelles without disulfide linkages, due to much more effective endosomal escape based on the PEG detachment in endosome. These findings suggest that the PEG-SS-P[Asp(DET)] micelle may have promising potential as a nonviral gene vector exerting high transfection with regulated timing and minimal cytotoxicity.     

Synthesis,Characterization, and Catalytic Activity of a Cubic [Mo3S4Pd] Cluster Bearing Bulky Cyclopentadienyl Ligands

A cubic metal-sulfur cluster containing three Mo ions and a Pd ion, [Cp^SiEt3₃Mo₃S₄Pd]Cl ( Mo₃Pd , Cp^SiEt3=C₅Me₄SiEt₃), was synthesized by the incorporation of the Pd ion into a Mo₃S₄ cluster [Cp^SiEt3₃Mo₃S₄] ( Mo₃ ). Mo₃Pd was characterized by ¹H NMR, UV-vis, X-ray crystallography, and cyclic voltammetry measurements. The electrochemical measurements demonstrated reversible one- and two-electron reduction processes for Mo₃Pd , which suggested potential catalytic activity for two-electron substrate reductions such as hydrogen evolution reaction. Controlled potential electrolysis in the presence of Mo₃Pd and trifluoroethanol in THF solvent displayed H₂ formation with a constant current over 60 min. The amount of generated H₂ by Mo₃Pd was two times higher than Mo₃ , indicating the catalytic activity facilitated by the Pd center. The mechanism of the catalytic cycle was determined by density functional theory.