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Molecular mechanics calculations of rearranged cholestenes revealed that diacholest-13(17)-enes with 10α stereochemistry are more stable than their 10β counterparts and that a partly rearranged sterene with a Δ 8 double bond and 10β, 14β stereochemistry (compound 7) is relatively stable at thermodynamic equilibrium. The calculated data are in good agreement with sedimentary and experimental data and thus reinforce recent propositions for early-stage diagenesis of steroids.

The chemical composition of a fossil resin from a Miocene outcrop in Brunei, South East Asia, is compared with its extant counterpart dammar, obtained from trees of the family Dipterocarpaceae, to establish the nature of the precursor of bicadinanes. The alcohol soluble fractions of the resins consist of functionalised triterpenoids and a small amount of sesquiterpenoids. None of the compounds present in this fraction bears any structural relation to bicadinanes. The alcohol insoluble fractions of the resins consist of a polymer based on cadinene. A structure for this polymer is proposed. Heating the polymer in dammar resin resulted in the formation of monomeric, dimeric, and trimeric cadinenes. It is thought that the naturally occurring bicadinanes result from dimeric cadinenes upon cyclisation.

In a study on the diagenesis of carbohydrates in a recent stromatolitic deposit (Solar Lake, Sinai) monosaccharides are quantitated after mild acid hydrolysis and gas chromatographic analysis as alditol acetates. From the depth profiles of the individual monosaccharides relative to the total organic carbon three categories of carbohydrates can be distinguished. The behaviour of the various categories upon burial is discussed in terms of their potential to become a part of the organic matter that survives geological periods. The distribution patterns of especially the mono- O -methyl monosaccharides at various depths are characteristics for the bacterial communities present in the corresponding parts of the sediment column.

Lipids present in a recent marine sediment were extracted, derivatized and analysed by GC and GCMS, without preseparation. This combination of methods offers the possibility to determine various classes of lipids simultaneously. Selective chemical treatment prior to the total lipid extraction, enables the determination of the mode of occurrence in the sediment and might yield more appropriate information about the origin of individual lipid moieties released. The significant relative abundancies of β-hydroxy fatty acids and the structural features of these acids among the lipids released after acid treatment point to the presence of bacterial cell wall material in the sediment sample. This suggestion was supported by a separate isolation of bacterial cell wall lipopolysaccharide.

A model for the mechanism of the molecular-sieve effect in polyacrylamide gel electrophoresis is presented for low gel concentrations. From mobility measurements at different gel concentrations, the model gives radii for protein molecules which are in good agreement with the values calculated from the known molecular weights.

Loliolide, isololiolide and dihydroactinidiolide are encountered in a recent marine sediment; they are probably photo-oxidation products of algal carotenoids.

The total organic matter of a recent marine diatomaceous ooze is studied by analysis of its water and acid extracts and residues. The extraction data relative to the total organic carbon reveal major contributions of carbohydrates (22%), “volatiles” (12%) and proteins (11%) and a smaller contribution of lipids (4%) and volatile fatty acids (1%). The residual organic carbon (50%) mainly shows aliphatic characteristics. Among the compounds identified in the extracts some with an algal and others with a bacterial origin are distinguishable.

This paper describes simulation experiments in which glucose and cellulose were reacted with polysulphide and hydrogen sulphide at ambient temperatures in an aqueous environment. Organic sulphur containing compounds were formed that yield several thiophenes upon pyrolysis/evaporation. The experiments show that interaction of carbohydrates with hydrogen sulphide or polysulphides is a possible way for carbohydrates to react in very recent sediments. From the results of this study it can be concluded that carbohydrate carbon can be preserved in sediments in a form that is resistant to microbial attack and that will have a greater potential for survival during diagenesis than the carbohydrate precursor.

Two-dimensional 1H and 13C shift-correlated NMR experiments have been used for the unambiguous assignments of all proton and carbon chemical shifts of two cadinanes and bicadinane.

The identification of naturally methylated neutral monosaccharides in acid hydrolysates as their alditol acetates requires appropriate standards. The availability of such standards also facilitates the analysis of complex mixtures of partially methylated alditol acetates (PMAAs) which appear upon methylation analysis of polysaccharides. For this purpose the alditols of eight common monosaccharides have been partially methylated using the Haworth methylation. The resulting mixtures of partially methylated alditols have been acetylated and analysed by capillary gas chromatography, gas chromatography—electron impact mass spectrometry and gas chromatography—chemical ionization mass spectrometry. Identification of the obtained PMAAs is further elaborated by reduction of the aldoses with sodium borodeuteride and the use of partially methylated aldoses or disaccharides.

Relative differences in free energy of 32 cholestene isomers have been calculated by molecular mechanics using the MM2 empirical force field with adjusted increments for sp 2 hybridised carbon atoms. Based on the results and on a reinspection of the literature it has been concluded that some steps in the previously proposed early diagenetic pathways of steroid diagenesis have to be reconsidered; double bond isomerizations via secondary carbocations are not considered likely to occur in nature. To explain in an alternative way the sterene/sterane distribution patterns observed in Recent sediments a limited isomerization ( via tertiary carbocations only) occurring simultaneously with a selective reduction is proposed.

A qualitative and partly quantitative survey of the carbohydrates encountered in acid hydrolyzates of some recent marine sediments reveals the presence of a large variety of known and hitherto unknown monosaccharides. Apart from the well known major monosaccharides a great number of minor components (notably O -methyl and deoxy monosaccharides) are encountered. These minor components are considered to originate from bacteria. Since significantly larger amounts of major monosaccharides are encountered in carbohydrates associated with bacterial cell-walls the greater part of the carbohydrate carbon in these sediments is ascribed to these structures. Superimposed on the bacterial contribution the characteristics of the carbohydrates originating from the primary producers are recognizable. The results indicate that bacterial biopolymers formed by de novo synthesis in the sediment should be considered as a potential source for the insoluble organic matter in these sediments.

A structural study of the toxic antibiotic bongkrekic acid (BA) has been performed. From chemical and spectroscopic evidence obtained for the acid and the totally reduced acid (HBA) we propose the following formula: 8-{2-(2-carboxy-5-methylcyclopent-2-en-1-ylidene)ethyl}-6-methoxy-2,5-dimethylhexadeca-2,4,9,12(13)-tetraenedoic acid (XXV).

A mathematical expression for the plate height in polyacrylamide gel electrophoresis is derived on the basis of the conservation of mass. Comparison of the theoretical with the experimental values justifies the assumption that diffusion and the velocity profile due to the electrical heat production are the main causes of peak broadening in polyacrylamide gel electrophoresis. Some applications of the theory to the optimization of gel electrophoresis experiments and to the estimation of the homogeneity of protein preparations are described.

Experiments to study time of insecticide application in relation to control of the European corn borer ( Pyrausta nubilalis (Hbn.)) were carried out at Ankeny, Iowa, in 1951-56. Two applications of DDT gave significantly better borer control than one application in all experiments. Each year the best control was obtained following applications when egg laying was almost completed. The minimum points on regression curves represented the estimated optimum treatment dates. Criteria used for predicting time of insecticide application, as they existed on the dates of optimum treatment, were compared with the recommended or suggested criteria. In 5 out of 6 years the number of borer-degree days on the date of optimum treatment was below the suggested 1100, averaging about 900. A tassel bud-plant height ratio of 35 appeared to be more suitable than the recommended range of 30 to 50. Except for 1 year plants in plots with the best borer control were consistently taller than the recommended 35 inches. Plant height and unhatched egg masses were found to be unreliable. Data on moth emergence were consistent with recommendations; however, this criterion is unsuitable for use by the average grower. The recommendation to treat when 75% of the plants show evidence of recent feeding in the whorls was the most rapid and simple to use.

The preparation, isolation and purification of the toxic antibiotic bongkrekic acid (BA), produced by Pseudomonas cocovenenans on partially defatted coconut are described. It has been shown that BA is a branched unsaturated tricarboxylic acid with a gross formula of C 28 H 38 O 7 . The presence of three methyl groups, one methoxyl group, one ring system and six double bonds—two isolated and two pairs of conjugated double bonds, both conjugated with a carboxyl group—is proved.

From NMR and MS studies, a new structure is proposed for the toxic antibiotic bongkrekic acid (BA), which is given by the formula: 3-carboxymethyl-17-methoxy-6,18,21-trimethyldocosa-2,4,8,12,14,18,20-heptaenedioic acid.

It is generally accepted that saturated polycyclic hydrocarbons such as steranes and triterpanes, present in crude oils and sediments, originate from naturally occurring steroids and triter-penoids. The occurrence of individual steranes and triterpanes can be used to relate the oil or sediment sample to the biological material from which it is derived. All previously known saturated C30 pentacyclic hydrocarbons could be related to a naturally occurring triterpenoid. Here we report that the structure of a novel C30H52 pentacyclic isoprenoid hydrocarbon present in some Far Eastern crude oils has been established as 2,6a,12-trimethyl-4,9-diisopropyl-perhydrobenzo[de]naphthacene by joint application of Chromatographie methods, mass spectrometry (MS), nuclear magnetic resonance (NMR), molecular mechanics and X-ray diffraction. As far as we know, this is the first report of the occurrence in nature of a pentacyclic C30 isoprenoid compound with a perhy-drobenzo[de]naphthacene skeleton. It can be considered as a dimer of the sesquiterpane cadinane. A biosynthesis of the skeleton by direct cyclization of squalene seems impossible in this case.