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The near ultraviolet and visible light (VL) impinging at an intensity of 2–5 × 10(2) J s-1 m-2 for 2–5 h kills the mitotic and the early S-phase (0- to 15-min-old) amoebae. At the mid- and late S-period only a fraction of cells are killed by VL and G2 phase cells are quite resistant. Amoebae of all cell cycle stages show a delay in the first mitotic division. DNA synthesis, as measured by [3H]thymidine incorporation, is depressed in the VL-exposed early-S amoebae. A concurrent but temporary inhibition in [3H]leucine incorporation also occurs in these cells. However, no significant change in [3H]uridine incorporation has been found. To localize the site of lethal damage, nuclear transplantation studies were undertaken between the control amoebae and the amoebae treated with VL. The nucleus of a VL-exposed early S-phase cell recovers when transplanted immediately after VL exposure into an enucleate G2 cytoplasm but dies if grafted into an enucleat S-phase cytoplasm. The therapeutic effect of the G2 cytoplasm, although at a lower level, is also evident even when the treated early S-phase nucleus is implanted 20 h later, but not after 48 h, into the G2 cytoplasm. The amoeba cytoplasm shows resistance to VL-irradiation, can accept a control nucleus from any cell cycle stage, and function normally. The G2 nucleus also remains apparently unaffected to VL exposure and can survive when it is transfered to the control cytoplasm of any cell-cycle phase. All these findings are discussed in the light of the possible existence of a repair system against VL-induced damage in the G2-phase amoeba.

Application of 100 pounds N per acre gave optimum yield of rice, provided plants did not lodge before heading. Pre‐heading lodging reduced level of nitrogen consumption and response and the yield. Lodging seemed to be a physiological phenomenon rather than a varietal character. It originated from structural weakness development in culm tissues and was caused primarily by deeper submergence of plants during vegetative growth aided by high nitrogen concentration in soil.

Several mannans from yeasts give proton magnetic resonance spectra with distinctive H-1 signals at higher field than τ 4.55. A number of these mannans were investigated polarimetrically and each has a specific rotation corresponding to a mixture of α- and β-D-linkages. Four were partially hydrolyzed and shown to have most of the α-linkages in the main chains and the β-linkages in the side chains. Detailed structural investigations showed that the Pichiapastorismannan probably has an α-(1→6)-D-manno-pyranosyl main-chain substituted in the 2-positions with a substantial proportion of O-α-D-mannopy-ranosyl-(1→2)-O-β-D-mannopyranosyl-(1→2)-O-β-D-mannopyranosyl-(1→2)-O-α-mannopyranosyl side-chains (1). The related mannan from Citeromycesmatritensishas a similar main-chain, which is substituted in the 2-positions by α-D-mannopyranosyl units and β-(1→2)-pyranose-linked D-mannotriosyl and perhaps mannobiosyl side-chains (2).

Some di-O- and tri-O-methylmannoses which are unknown or difficult to prepare have been synthesized. These and the other isomers, which can arise from methylation–fragmentation analyses of mannofuranose- and mannopyranose-containing polysaccharides can be used as gas–liquid chromatographic (g.l.c.) standards. A system has been devised in which methylation fragments are fractionated on a cellulose column into di-O-, tri-O-, and tetra-O-methylmannose fractions, which are then analyzed individually by g.l.c. following conversion to suitable derivatives.

The reduction of hexofuranose and hexopyranose acetals with LiAlH4–AlCl3(1:1, probably AlH2Cl) to the corresponding ethers proceeds in similar fashion as that of simple acetals and ketals (Scheme I) (refs. 1–7). Certain O-methyl and O-benzyl derivatives, not readily obtainable otherwise, are conveniently synthesized from appropriate acetals in this way. Cyclic orthoesters of glucofuranose may be selectively reduced to acetals; the steric course of such reduction has been shown unequivocally in the case of orthoformates (Scheme II). Of several cleavable groups, the ease of hydrogenolysis is (a) cyclic orthoester > isopropylidene ketal, cyclohexylidene ketal > benzylidene acetal > ethylidene acetal > formal and (b) 5,6-O-linked or 3,5-O-linked acetal or ketal > 1,2-O-linked acetal or ketal.

AbstractA study of the geological history of a small dioritic mass near Gairloch has revealed the presence of rock types and structural elements not represented in most of the Lewisian of the district. Coarse grained diorite, showing intrusive relations to granulitic rocks of possible sedimentary derivation, has been foliated and subsequently intruded by microdiorite during pre-Laxfordian episodes. The Little Sand mass has subsequently been involved, probably as a thrust slice of basement, in the sequence of Laxfordian (about 1,500 m.y.) structural and metamorphic episodes which affected the more common Lewisian metasediments and metabasites.

Carbon-13 Fourier transform n.m.r. spectra of the biopolymer, heparin, are described. The proton-decoupled spectrum corresponds to that of a molecular structure based on 12 carbon atoms, and the observed chemical shifts are shown to be consistent with a previously-proposed alternating sequence consisting of (1 → 4) linked residues of α-D-idopyranosyluronic acid 2-sulfate and 2-deoxy-2-sulfamino-α-D-glucopyranosyl 6-sulfate. Line-broadening of the C-6 signal of the latter residue indicates that spin–spin relaxation of the 13C nucleus of this sulfated primary carbinol group is more effective than for the 13C nuclei of the sugar rings. Among model compounds utilized for assignment of the signals from heparin is a disaccharide, 4-O-(α-L-idopyranosyluronic acid 2-sulfate)-2,5-anhydro-D-mannose 6-sulfate, prepared in 65% yield by deaminative degradation of heparin.

Thymine starvation of E. coli B/r resulted in a decrease in single-strand molecular weight of DNA, as determined by sedimentation in alkaline sucrose gradient. This decrease could not be compensated by 60 min incubation in growth medium after thymine starvation. The strand breaks in DNA induced by x-irradiation could not be repaired in growth medium in 60 min when the cells were prestarved of thymine. Thymine-starved cells also showed more strand breaks in DNA, at the same levels of survival, due to x-irradiation than the cells that were not so starved.

The reduction of α-aminoadipate to α-aminoadipic δ-semialdehyde by a cell-free extract of Saccharomyces is shown to be a three-step process. First the amino acid reacts with ATP to form an adenylyl derivative. Then the adenylyl derivative of α-aminoadipate is reduced in the presence of NADPH. In the third step the reduced adenylyl derivative of the amino acid is cleaved to form α-aminoadipic δ-semialdehyde. The presence of Mg2+is necessary for the first and second steps. The third step does not need any cofactors. The product of the first step was isolated by chromatography after incubating the cell-free extract of Saccharomyces with α-aminoadipate, ATP and Mg2+. The isolated product was identified as an adenylyl derivative of α-aminoadipate and could be converted into α-aminoadipic δ-semialdehyde under the stated experimental conditions. The product of the second step was too unstable to be identified.

The effect of treatment of purified cholera enterotoxin with acid at pH 2.0 for 1 h followed by neutralization of the acid on the biological activity of the toxin has been studied. It was found that the material loses 85 to 96% of its skin permeability activity and this loss is neither reversed nor increased after 28 days of storage at 5 to 10 C. Other biological properties such as diarrheagenic activity, lipolysis-stimulating activity, and the lethal dose for mice remain unaffected by acid treatment. These observations indicate that the skin permeability activity is more sensitive to relatively minor changes in molecular structure than are the diarrheal, lipolytic, and mouse lethality activities.

A pectic material has been isolated from the bark of Abiesamabilis(Dougl.) Forbes in a yield of 2%. On hydrolysis it yielded D-galacturonic acid, D-galactose, and L-arabinose in a ratio of 85:4:11, and also traces of rhamnose. The product, when submitted to several conventional fractionation methods, appeared homogeneous. Further resolution could be effected by acidification of an aqueous solution of the pectin, followed by ultracentrifugation. The insoluble portion (50%) was an electrophoretically homogeneous galacturonanwith [α]D + 246°. The material remaining in solution (30%), here referred to as a pecticacid, had [α]D + 225° and on hydrolysis gave D-galacturonic acid, D-galactose, and L-arbabinose in a ratio of 74:7:19, as well as traces of rhamnose.The structure of the galacturonan was established by partial hydrolysis and methylation. It consisted of α-D-galacturonic acid residues linked together by (1 → 4)-glycosidic bonds to a linear macromolecule. The same techniques were applied to the pectic acid. While a unique structural formula could not be assigned in this case, one probable alternative involved a framework of (1 → 4)-linked α-D-galacturonic acid residues together with a few residues of 1,2,4-linked L-rhamnose. Some of the galacturonic acid units carried at C-2 and C-3 side chains which were terminated by D-galactopyranose and L-arabinofuranose residues. A few of the latter also occurred as inner units, probably in the side chains. This appears to be the first time a pectic material has been resolved into a galacturonan and a pectic acid containing the four sugar residues usually found in pectins. It is probable that the pectin occurring to a limited extent in wood has a similar composition.

Hydroxylysine acts as a growth inhibitor of Saccharomycesfor a certain period of time. The inhibition is concentration-dependent and is reversed by a small amount of lysine in the medium. After the growth-inhibitory period, the wild-type cells are able to grow rapidly even in the presence of hydroxylysine. Both lysine auxotrophs and wild-type cells are unable to utilize hydroxylysine in place of lysine. Hydroxylysine, mimicking lysine, controls the biosynthesis of lysine and thereby limits the availability of biosynthetic lysine to the cells. Hydroxylysine affects the biosynthesis of lysine at a number of enzymatic steps. Accumulation of homocitric acid, the first intermediate of lysine biosynthesis, in the mutant strains 19B and A B9 is reduced significantly in the presence of hydroxylysine. Hydroxylysine, like lysine, exerts a significant inhibition in vitro on the homocitric acid-synthesizing activity. Enzymes following the α-aminoadipic acid step respond in a noncoordinate fashion to hydroxylysine. Level of the enzyme saccharopine reductase, but not of α-aminoadipic acid reductase or saccharopine dehydrogenase, is reduced significantly. These regulatory effects of hydroxylysine are similar to those observed for lysine.

Aconitaseless glutamic acid auxotroph MO-1-9B of Saccharomycesgrew in glutamic acid-supplemented minimal medium, but failed to grow when glutamic acid was substituted by proline, arginine, ornithine, or glutamine. This mutant was also unable to utilize lactate or glycerol as a carbon source. Under a glutamic acid-limiting condition, by using acetate-1-14Cas tracer, the mutant accumulated rather large amounts of 14C-citric acid and 14C-succinic acid when compared with the wild-type strain. Under excess glutamic acid supplementation, accumulation of citric acid and succinic acid was considerably reduced. When 14C-glutamic acid-(U) was used as tracer, 14C-α-ketoglutaric acid, 14C-citric acid, and 14C-succinic acid were accumulated in the mutant. The citric acid peak was the largest, followed by α-ketoglutaric acid and succinic acid. In the wild-type strain under similar conditions, only small amounts of 14C-citric acid and 14C-succinic acid and no 14C-α-ketoglutaric acid were accumulated.