Automatic reaction calorimeters were developed. Enthalpies of hydration or hydrolysis were determined for polyoxygenated methanes, ketals, acetals, orthoesters, and alkenes. Trifluoroacetolysis of alkenes was carried out. Enthalpies of acetolysis and comb...

The synthesis of endo- and exo-norbornyl-l-5,6-d/sub 2/ pbromobenzenesulfonates is deicribed. The rate constants of the acetolysis were measured and an isotope effect was observed in the reaction of the exo-isomer. The result indicates that the 1,3-hydride shift occurs in the rate determining step. (auth)

The pi-(arene)chromium tricarbonyl complexes of 2-phenyl-2-methyl-1-propyl(neophyl) and p-methoxy-, p-methyl-, and m-methylneophyl methanesulfonates have been prepared and their acetolysis rates and products determined. At 75C the complexed derivatives ar...

The kinetics of the acetolysis of trans-2-Hlg-cyclopentyl p-toluenesulfonates (Hlg=Br, I), which is realized with anchimeric assistance from the Br and I atoms, were studied. It was established that the degree of anchimeric assistance from the ..beta.. substituents changes little in the transition from trans-2-substituted cyclopentyl to the trans-2-substituted cyclohexyl ...

Internal return associated with the acetolysis of 3-phenyl-2-butyl p-toluenesulfonate results in racemization of the unsolvolyzed ester. Thus recemization of the unsolvolyzed ester is a measure of total ion pair return. The rate of randomization of the su...

A novel method for the preparation of 1,3,5-triacetyl-1,3,5-triazacyclohexane (TRAT), an important intermediate for the preparation of 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), was developed. Based on the knowledge of the mechanism of acetolysis of he...

Rates of solvolysis of 2-phenylethyl (Ia), b 2/ (Ic) p-toluenesulfonates were determined in formic and in acetic acid. In formolysis Ia and Ic react at the same rate, but Ia reacts 17 plus or minus 2% faster than Ib. In acetolysis small effects are observed with both deuterated com. pounds: Ia is 3 plus or minus 1% faster than Ib and 4 plus or minus 3% faster ...

The amounts of randomization of sulfonate oxygen atoms associated with ion-pair return for acetolysis of 18O-labeled threo-3-phenyl-2-butyl and endo-bicyclo(3.2.1)octan-2-yl p-toluenesulfonates have been determined. In each system the ratio of oxygen equi...

Controlled acetolysis of yeast mannans yields mixtures of oligosaccharides with (1?2) and (1?3) linkages between the mannose units, whereas the less stable (1?6) linkages of the polysaccharide backbone are cleaved. The �fingerprints,� obtained by gel filtration of the oligosaccharide mixtures, can be used to distinguish between the different yeast mannans. The general ...

Automatic reaction calorimeters were developed. Enthalpies of hydration or hydrolysis were determined for polyoxygenated methanes, ketals, acetals, orthoesters, and alkenes. Trifluoroacetolysis of alkenes was carried out. Enthalpies of acetolysis and combustion of cyclopropane derivatives were also determined. Molecular mechanics calculations were carried out for ketones and ...

The pi-(arene)chromium tricarbonyl complexed methanesulfonates 2-phenylethyl (2-OMs), 2-phenylethyl-1,1-d2 (4-OMs), and 2-phenyl-1-propyl (dl-6-OMs) have been prepared and their acetolysis and formolysis rates and/or products compared with those of the no...

Solvolysis of bicyclo(2.2.2)octan-2-yl (I-OTs) and exo-bicyclo(3.2.1)octan-2-yl p-toluenesulfonates (III-OTs) gives binary mixtures of (2.2.2) and exo-(3.2.1)isomers. Optical purities of both isomers have been determined for acetolysis and hydrolysis (80%...

The isotope effects of deuterium on substituted neophyl ester solvolysis rates were studied to determine the influence of phenyl participation on isotope effects, and to determine the relationship of transition state structure to solvent, substituent, and leaving group. The $alpha$-d isotope effects and the solvolysis rates for the acetolysis and trifluoroacetolysis ...

Structure of the glucomannan isolated from the cell walls of Candida utilis has been investigated using acetolysis fragmentation, methylation analysis and NMR spectroscopy. The structure of the glucomannan resembles that of the cellular mannans of other Candida species, except that the longer tetra- and pentassacharide side-chains are terminated with a glucosyl residue. ...

In mature megaspores of Selaginella diffusa (C. Presl) Spring the units of the exospore are ordered and become unordered toward the outer and inner surfaces. The exospore surface is coated with silica at maturity. The insertion of the future gap begins in early stages with formation of many minigaps within the inner part of the exospore distally. The mesospore, like the exospore, is resistant to ...

The synthesis of cyclopropylmethyl-1,1-d/sub 2/,-2-d,-3,3-d/sub 2/, and - 3,3,4,4-d/sub 4/ benzenesulfonates is described. Acetolysis and ethanolysis rates were measured and it was found that the first two compounds solvolyze more slowly and the last two more rapidly than the undeuterated analogs. It was also found that the isotope effects are more pronounced in ...

The immunochemical properties and structural features of D-mannans from two Candida parapsilosis strains were studied. Weak cross-reactivity of D-mannans with antisera produced to C. parapsilosis strains was observed, as well as significant differences in the mannans structures were found by means of methylation analysis, acetolysis and 1H-NMR spectroscopy. In view of the ...

In the reaction of formaldehyde with 2-methyl-5,6-dihydropyran and of acetaldehyde with 4-methyl-5,6-dihydropyran under Prins reaction conditions, compounds with 1,3-dioxane structure, the corresponding trioxadecalins, are formed as the main products. 4-Methyl-5,6-dihydropyran reacts with CH/sub 2/O anomalously with the preferential formation of diols, cis- and ...

The mannans of Saccharomyces chevalieri, S. italicus, S. diastaticus, and S. carlsbergensis, were acetolyzed, and the fragments were separated by gel filtration. All gave similar acetolysis fingerprints, which were distinguished from S. cerevisiae by the presence of a pentasaccharide component in addition to the mono-, di-, tri-, and tetrasaccharides. All oligosaccharide ...

Absence of a substantial pretracheophyte fossil record for bryophytes (otherwise predicted by molecular systematics) poses a major problem in our understanding of earliest land-plant structure. In contrast, there exist enigmatic Cambrian-Devonian microfossils (aggregations of tubes or sheets of cells or possibly a combination of both) controversially interpreted as an extinct group of early land ...

Absence of a substantial pretracheophyte fossil record for bryophytes (otherwise predicted by molecular systematics) poses a major problem in our understanding of earliest land-plant structure. In contrast, there exist enigmatic Cambrian�Devonian microfossils (aggregations of tubes or sheets of cells or possibly a combination of both) controversially interpreted as an extinct group of early land ...

Fluorescent in situ hybridization (FISH) using taxon-specific, rRNA-targeted oligonucleotide probes is one of the most powerful tools for the rapid identification of harmful microorganisms. However, eukaryotic algal cells do not always allow FISH probes to permeate over their cell walls. Members of the pathogenic micro-algal genus Prototheca are characterized by their distinctive cell-wall ...

The Arabidopsis thaliana MALE STERILITY 2 (MS2) gene product is involved in male gametogenesis. The first abnormalities in pollen development of ms2 mutants are seen at the stage in microsporogenesis when microspores are released from tetrads. Expression of the MS2 gene is observed in tapetum of wild-type flowers at, and shortly after, the release of microspores from tetrads. The MS2 promoter ...

The glycosylphosphatidylinositol membrane anchor of human placental alkaline phosphatase was isolated by exhaustive proteolysis followed by hydrophobic interaction chromatography. The resulting glycosylphosphatidylinositol-peptide was subjected to compositional analysis and chemical and enzymic modifications. The neutral-glycan fraction, prepared by dephosphorylation followed by HNO2 deamination ...

Background and AimsAlthough orbicular functions are still a matter of debate, they are considered by most authors to be exclusively formed by a secretory tapetum. However, the presence of orbicules on a peritapetal membrane associated with a plasmodial tapetum has been described for Abutilon pictum (Malvaceae) in a previous study. Thus, studies on other species of Malvaceae are necessary to ...

Knowledge about the botanical source of honey is very important for the beekeeper while it indicates adequate and abundant supply sources of nectar and pollen for the bees, thus contributing toward improved yield. The present study means to identify the pollen types occurring in 58 samples of honey produced in two states of the northeastern region of Brazil, Piau� (38 samples) and Cear� (20 ...

This study was carried out in the Parque Municipal das Arauc�rias, located in the municipality of Guarapuava (PR) from May (06) to April (07). Its aim was to investigate which plants are used by Megachile (Moureapis) sp in provisioning of larvae, and to verify if this bee is oligolectic or polilectic. The collection of the plants was carried out during the bees activity period and in an area ...

We report the initial characterization of glucans present in the periplasmic space of Pseudomonas syringae pv. syringae (strain R32). These compounds were found to be neutral, unsubstituted, and composed solely of glucose. Their size ranges from 6 to 13 glucose units/mol. Linkage studies and nuclear magnetic resonance analyses demonstrated that the glucans are linked by beta-1,2 and beta-1,6 ...

We report the initial characterization of glucans present in the periplasmic space of Pseudomonas syringae pv. syringae (strain R32). These compounds were found to be neutral, unsubstituted, and composed solely of glucose. Their size ranges from 6 to 13 glucose units/mol. Linkage studies and nuclear magnetic resonance analyses demonstrated that the glucans are linked by beta-1,2 and beta-1,6 ...

Symplocarpus L. (Araceae) is a disjunct genus including S. foetidus (L.) Nutt. var. latissimus (Makino) S. Hara, S. nipponicus Makino, and S. nabekuraensis Otsuka & K. Inoue in temperate eastern Asia; S. egorovii N. S. Pavlova & V. A. Nechaev in the Russian far east; and S. foetidus (L.) Nutt. in temperate northeastern North America. For the first time, pollen morphology of Symplocarpus ...

A study of the gamma -ray-induced mutual grafting of styrene onto cellulose acetate (combined acetic acid, 52.8%) showed that cellulose acetate enhances the rate of polymerization of styrene. Dilution of the monomer with benzene accelerates the polymerization, with a maximum effect occurring at 60 mole% styrene. Grafting efficiency increases as monomer concentration increases also ...

The graft copolymerization of cellulose and styrene was accelerated by immersing the cellulose in H/sub 2/0/sub 2/ solution during gamma irradiation. The number of active sites such as hydroperoxides was estimated by the ferrous ion method. A correlation between the number of active sites and the rate of grafting is shown. The acetylation of the grafted cellulose--styrene polymer was ...

We conducted a structural analysis of the antigenic cell wall mannoprotein (mannan) isolated from Candida kefyr (formerly Candida pseudotropicalis) IFO 0586. The result of two-dimensional homonuclear Hartmann-Hahn analysis of this mannan indicates that the molecule is constructed from alpha-1,2- and alpha-1,6-linked mannopyranose residues. Upon alkali treatment (beta-elimination reaction), this ...

Lipopolysaccharide (LPS) is the first defense against changing environmental factors for many bacteria. Here, we report the first structure of the LPS from cyanobacteria based on two strains of marine Synechococcus, WH8102 and CC9311. While enteric LPS contains some of the most complex carbohydrate residues in nature, the full-length versions of these cyanobacterial LPSs have neither heptose nor ...

Cellobiohydrolases I(D) and II were purified by ion exchange chromatography from an extracellular culture filtrate of Tricoderma reesei QM 9414. Neutral sugar composition of each was determined by gas-liquid chromatographic analysis of the peracetylated alditol and aldononitrile acetate derivatives of sugars released by either reductive US -elimination or acid hydrolysis. The alkaline ...

Cellulose acetate film was sealed in a glass tube that contained styrene monomer and solvent and then exposed to an 800-C Co/sup 60/ gamma -radiation source. After irradiation, the film was removed and washed with benzene, a solvent for the styrene homopolymer. The film was then extracted with acetone to remove the ungrafted cellulose acetate. The chemical composition of the graft ...

The predators Hippodamia convergens Gu�rin-Men�ville (Coleoptera: Coccinelidae) and Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae), are frequently observed on vegetable crops, especially on tomato plants, as well as on flowers of several plants around crop fields. It is well known that when predators feed on pollen and nectar they can increase their longevity and reproductive capacity. ...

The bromine atoms of the hexabromo calixarene derivative 3 were replaced by other groups under S(N)1 conditions, allowing the facile synthesis of calix[6]arene derivatives incorporating identical functionalities at all bridges. Heating at reflux a mixture of 3 and the appropriate alcohol incorporated primary and secondary alkoxy substituents. Hydride abstraction was observed when the reaction with ...

[3H]Mannose- and [3H]glucosamine-labeled lactosamine-type glycopeptides of Semliki Forest virus membrane proteins were stripped of their fucose, sialic acid, galactose and distal N-acetylglucosamine residues and subsequently digested with endo-beta-D-N-acetylglucosaminidase D from Diplococcus pneumoniae. Two products were obtained, a neutral tetrasaccharide and a residual glycopeptide fraction. ...

The galactomannan (GM) produced extracellularly by Aspergillus fumigatus has been purified by a double sequential hydrazine-nitrous acid treatment of the ethanol precipitate of the culture filtrate. Nuclear magnetic resonance and gas-liquid chromatography-mass spectrometry analysis have been performed on intact GM, acid-hydrolyzed GM, and oligomers resulting from the ...

The dolichyl pyrophosphates of ..beta..-Manp-(1..-->..4)-..beta..-D-G1cpNAc-(1..-->..4)-..cap alpha..-D-GlcpNAc (I), ..cap alpha..-D-Manp-(1..-->..3)-..beta..-D-Manp-(1..-->..4)-..beta..-D-GlcpNAc-(1..-->..4)-..cap alpha..-D-GlcpNAc (II), and ..cap alpha..-D-Manp-(1..-->..6)-..beta..-D-Manp-(1..-->..4)-..beta..-D-GlcpNAc-(1..-->..4)-..cap alpha..-D-GlcpNAc (III) were ...

The structures of N-linked oligosaccharides from various Leishmania life-cycle stages and species have been investigated in order to elucidate differences which may be correlated with virulence or tissue tropisms. The structure of gp63 glycans from L major log- and stationary-phase promastigotes were elucidated and compared with the total membrane associated oligosaccharides from five Leishmania ...

Secondary deuterium isotope effects in ethanolysis of 3$beta$- cholestanyl-3-d$sub 1$ brosylate (2e), 3$alpha$-cholestanyl-3-d$sub 1$ brosylate (2a), 3$beta$-cholestanyl-2,2,4,4-d$sub 4$ brosylate (3e), 3$alpha$-cholestanyl- 2,2,4,4-d$sub 4$ brosylate (3a), 3$beta$-cholestanyl-2$alpha$-d$sub 1$ brosylate (4e), 3$alpha$-cholestanyl-2$alpha$-d$sub 1$ brosylate (4a), and 3$alpha$- ...

We describe the environment effects on the amount and quality of resources collected by Melipona rufiventris Lepeletier in the Atlantic Forest at Ubatuba city, S�o Paulo state, Brazil (44�48'W, 23�22'S). Bees carrying pollen and/or nectar were captured at nest entrances during 5 min every hour, from sunrise to sunset, once a month. Pollen loads were counted and saved for ...

Proterozoic microfossils revealing the time of algal divergences Ma?gorzata Moczyd?owska-Vidal Uppsala University, Department of Earth Sciences, Palaeobiology, Villav�gen 16, SE 752 36 Uppsala, Sweden (malgo.vidal@pal.uu.se) Morphological and reproductive features and cell wall ultrastructure and biochemistry of Proterozoic acritarchs are used to determine their affinity to modern algae. The ...