Orientational ordering and dynamics of the hydrate and exchangeable hydrogen atoms in crystalline crambin

Deuterium nuclear magnetic resonance studies of crambin crystals grown from deuterated solvent (2H2O/CH3CH2O2H or H2O/C2H3CH2OH) are reported. The extent to which the hydrate and exchangeable hydrogen atoms are dynamically disordered are then determined from the size of the residual deuterium quadrupole couplings, qcc. Rapid molecular reorientation (tau c-1 greater than 10(5) s-1) reduces the magnitude of the quadrupole coupling from its static value (216 kHz for solid water). We find that the room temperature spectrum of crambin is dominated by two features: a sharp line with very small residual quadrupolar coupling less than 3 kHz, and a broad pattern with a quadrupolar coupling in the range 185 to 195 kHz. The former is indicative of very nearly isotropically reorienting deuterons, whereas the latter is somewhat narrower than that observed for the amide deuterons of poly-gamma-benzyl-L-glutamate and thus indicative of deuterons that are almost but not completely stationary. By considering the nuclear magnetic resonance spectrum intensities along with the amino acid sequence, X-ray structure and the manner in which quadrupole couplings are reduced by dynamics, we conclude that the nuclear magnetic resonance signal from most of the water molecules of hydration are contained in the sharp line, i.e. reorient nearly isotropically in the crystalline protein. Unlike bulk water, which freezes abruptly in the manner of a phase transition, the water of hydration in crambin has a broad freezing range from 180 to 250K, as evidenced by the decreasing intensity of the sharp line that disappears at 180K. At temperatures between 150 and 200K, a typical hydrate molecule reorients at a rate comparable to the quadrupole coupling, 10(4) s-1 to 10(5) s-1, a process that occurs in hexagonal ice in the range of 240 to 270K. At 140K, the hydrate is stationary, tau c-1 less than 10(3) s-1. Studies of the protein crystallized from solvent deuterated only at the non-exchangeable methyl group of ethanol confirm that ethanol is in the lattice and show that this solvate behaves in much the same way as the hydrate. The refined X-ray structure has identified four ethanol solvate molecules. The deuterium spectrum at room temperature has a well-defined residual pattern with qcc = 2.2 kHz, i.e. a small-order parameter consistent with nearly isotropically reorienting molecules. The spectrum width broadens substantially only at temperatures below 200K and achieves the characteristic spectrum of a rotating methyl group with stationary C-C axis at 140K.(ABSTRACT TRUNCATED AT 400 WORDS)     

Role of isovaleroyl lipids in channeling of sound in the porpoise melon

Physical properties (e.g. specific gravity, adiabatic compressibility and sound velocity) of lipids isolated from tissues from contiguous areas of the fatty melon of an echo-locating porpoise (Delphinus delphis) were determined to elucidate relations between lipid composition and structure, and sound transmission in the head. Lipid content varied greatly within the melon (13.6–77.6% of the tissue weight) and triacylglycerols (80–100%) were the major lipid components. This lipid class was composed of diisovaleroylglycerides (triacylglycerols containing two isovaleroyl moieties and a long-chain acyl moiety), monoisovaleroyldiacylglycerols and triacylglycerols consisting of long-chain acids. The lipid-rich (>45%) areas in the melon contained a high proportion (>45% of total triacylglycerols) of diisovaleroylglycerides. There were gradations of sound velocities within the melon; the lowest sound velocities were associated with high concentrations of diisovaleroylglycerides (<1400 m/s) and the highest with high concentrations of long-chain triacylglycerols. Assuming an average sound frequency of 75 kHz, and considering dimensions of melon (path length and width of 12–14 cm and 5 cm, respectively), a forward radiating lobe of 15–25 degrees is produced. Thus, the deposition of lipids of different acoustic properties in a three-dimensional matrix within the porpoise melon results in a lens for the projection of sound into the marine environment.     

Depletion of the spermatogonia from the seminiferous epithelium of the rhesus monkey after X irradiation

In unirradiated testes large differences were found in the total number of spermatogonia among different monkeys, but the number of spermatogonia in the right and the left testes of the same monkey appeared to be rather similar. During the first 11 days after irradiation with 0.5 to 4.0 Gy of X rays the number of Apale spermatogonia (Ap) decreased to about 13% of the control level, while the number of Adark spermatogonia (Ad) did not change significantly. A significant decrease in the number of Ad spermatogonia was seen at Day 14 together with a significant increase in the number of Ap spermatogonia. It was concluded that the resting Ad spermatogonia are activated into proliferating Ap spermatogonia. After Day 16 the number of both Ap and Ad spermatogonia decreased to low levels. Apparently the new Ap spermatogonia were formed by lethally irradiated Ad spermatogonia and degenerated while attempting to divide. The activation of the Ad spermatogonia was found to take place throughout the cycle of the seminiferous epithelium. Serum FSH, LH, and testosterone levels were measured before and after irradiation. Serum FSH levels already had increased during the first week after irradiation to 160% of the control level. Serum LH levels increased between 18 and 25 days after irradiation. Serum testosterone levels did not change at all. The results found in the rhesus monkey are in line with those found in humans, but due to the presence of Ad spermatogonia they differ from those obtained in non-primates.     

Improved synthesis of oligodeoxyribonucleotide using 3-methoxy-4-phenoxybenzoyl group for amino protection.

3-Methoxy-4-phenoxybenzoyl group has been used for the protection of exocyclic amino group of nucleosides. In case of 2'-deoxycytidine it has been found to be highly selective under controlled conditions. The N-protected derivatives of 2'-deoxyadenosine and 2'-deoxyguanosine have been found to be sufficiently stable towards acids minimising depurination under conditions of synthesis of oligodeoxyribonucleotide on solid support via phosphotriester approach. The high lipophilicity of the group and milder deprotection conditions are additional advantages.