Production of avermectin A2a and monoglycosides A2a and B2a by a strain ofStreptomyces avermitilis

A strain ofStreptomyces avermitilis producing almost predominantly avermectin A2a and monoglycosides A2a and B2a was described. Methods of analytical and preparative high performance liquid chromatography were used for comparison of chromatographic profiles and product isolation, respectively. Identification of isolated compounds was based on¹³C-NMR spectrometric results.     

A cDNA clone encoding a glycinin A1a subunit precursor of soybean.

A cDNA clone covering the whole coding region for a glycinin subunit precursor containing the A1a acidic subunit, one of the A2 family, has been identified from a library of soybean cotyledonary cDNA clones using a mixed oligonucleotide probe. Analysis of the cDNA insert revealed that it contained 1746 nucleotides of mRNA sequence with a 5'-terminal nontranslated region of 54 nucleotides, a signal peptide region corresponding to 19 amino acids, an acidic subunit region (A1a) corresponding to 291 amino acids followed by a basic subunit region corresponding to 185 amino acids, and a 3'-terminal nontranslated region of 207 nucleotides. By comparing the predicted protein sequence of this precursor with that of the legumin A precursor of pea, it was found that glycinin A2 subunit family appeared to be more closely related to the legumin than to the A3 subunit family, and that the evolutional rearrangement of glycinin genes has occurred.     

A Sustainability Assessment of a Biolubricant

A sustainability matrix has been developed at Shell Global Solutions to show the environmental, social, and economic impacts of a product. The approach aims to be quicker and more cost-effective than a conventional life-cycle assessment by focusing on specific areas of concern through the product life cycle and then comparing products by scaling their impacts relative to one another. It provides a way of making qualitative and quantitative assessment that gives a depth to the assessment beyond data analysis. The tool includes subjective judgment, which tends to reflect current thinking in the company. Once the tool has been fully tested on all product types, the indicators that are central to the process will be assessed by external stakeholders. This article describes the development of the sustainability assessment tool and presents an example that compares the sustainability of a biolubricant (an "environ-mentally acceptable" hydraulic fluid meeting Swedish Standard SS 15 54 34) with that of a conventional mineral-oil-based product. The tool provides a quick decision-making instrument to help Shell decide which products should be marketed for the business to continue on a sustainable path. The tool also provides a more detailed level of information if a more thorough assessment is necessary.     

A model of a thalamic neuron

We modify our recent three equilibrium-point model of neuronal bursting by a means of a small deformation of the nullclines in the x-y phase plane to give a model that can have as many as five equilibrium points. In this model the middle stable equilibrium point (e.p.) is separated from the outer stable and unstable e.ps by two saddle points. If the system is started at rest at the middle stable e.p. it has the following complex properties: A short suprathreshold current pulse switches the model from a silent state to a bursting state, or to give a single burst, depending on the choice of parameters. A subthreshold depolarizing current step gives a passive response at rest, but if the model is either constantly hyperpolarized or constantly depolarized, then the same current step gives different active responses. At a hyperpolarized level this consists of a burst response that shows refractoriness. At a depolarized level it consists of tonic firing with a linear frequency--current relationship. Hyperpolarization from rest is followed by post-inhibitory rebound. The model responds in a unique and characteristic way to an applied current ramp. These properties are very similar to those that have been recently recorded intracellularly from neurons in the mammalian thalamus. In the x-y phase plane our models of the repetitively firing neuron, the bursting neuron and the thalamic neuron form a progression of models in which the y nullcline in the subthreshold region is deformed once to give the burst neuron model, and a second time to give the thalamic neuron model. Each deformation can be interpreted as corresponding to the inclusion of a slow inward current in the model. As these currents are included so the associated firing properties increase in complexity.     

A Concept of a Pathology Institute

Scholarly achievement is the aim of a pathology institute. In a medical faculty it serves undergraduate, postgraduate teaching, practice and research. Historically, scholarly achievement in these fields has been promoted through the teaching responsibility of the university and hospital. With the increasing volume of work, knowledge and complexity of research, adequate performance in these fields is best obtained by limiting the volume of fixed duties for each individual. At the same time, depth of knowledge is gained by encouraging specialization to complement clinical specialties. This arrangement will guarantee that the teaching and research of the department are disease-oriented, which is the central theme of pathology. With a highly specialized staff there must be a core of intradepartmental conferences common to all staff and those in training. With this form of organization dedicated to the undergraduate and postgraduate teaching, the objectives of scholarly achievement in teaching practice and research will be obtained.     

S-trifluoroacetonyl-coenzyme A:a 19F analogue of acetyl-coenzyme A

S-Trifluoroacetonyl-coenzyme A has been synthesized in 87% yield by reaction of 1,1,1-trifluoro-3-bromopropanone with trilithium coenzyme A in presence of pyridine. The compound was characterized by its ultraviolet absorption spectrum and 1H and 19F nuclear magnetic resonance spectra. The alpha-methylene protons of the S-trifluoroacetonyl group exchanged with D2O and showed a pKa of 9.85 in S-trifluoroacetonylmercaptoethanol. S-Trifluoroacetonyl-coenzyme A is a competitive inhibitor of porcine heart citrate synthetase (Ki = 0.16 mM). It forms a binary complex with the enzyme and a ternary complex with enzyme/oxaloaetate binary complex, as evidenced ty the 19F shift. S-Trifluoracetonyl-coenzyme A and S-trifluoroacetonylmercaptoethanol form weak to moderately strong complexes with alpha-cyclodextrin and show little or no interaction with the methylglucose polysaccharide and lipopolysaccharides from Mycobacterium smegmatis [Smith, W. L., & Ballou, C. E. (1973) J. Biol. Chem. 248, 7118]. S-Trifluoroacetonylmercaptoethanol probably forms an inclusion complex with alpha-cyclodextrin because the interaction is reversed by compounds that do form inclusion complexes.     

A study on a vibratory model of a human body

This paper is concerned with the modeling of the human body as a spring mass system. Based on certain assumptions, an analysis for evaluating the mass and stiffness values of the model is developed. As an illustration of the modeling procedure, a 15-degree-of-freedom model of a male body is considered. The computed natural frequencies of the model are found to be within the range of available experimental values.     

A burrow of a little ground squirrel as a consortium

Structure of consortia as an animal community inhabiting a mammalian burrow with an example of the little souslik Spermophilus pygmaeus Pallas from Western Kazakhstan was studied. Species composition, numbers and distribution of invertebrates in different types of burrows and nests of the little souslik were examined on the background to their food dependencies on the host. The consortia is considered as a system of concenters around the host of burrow (center of community, CC). Recognized concenters are given with ranks based on food relations between invertebrate inhabitants and CC: concenter of I rank includes direct parasites and predators of CC, II rank is represented by consumers of dead bodies of the souslik and its life activity products; III rank includes predators and parasites of souslik's cohabitants, and concenter of IV rank encompasses animals, which use the burrow as a refuge only. Within limits of each concenter, a number of "rondos", groups of animals attributed to certain systematic category, for example ticks, gamasid mites, certain insect orders etc., may be recognized.     

Characterization of Esterase A, a Pseudomonas stutzeri A15 Autotransporter

Autotransporters are a widespread family of proteins, generally known as virulence factors produced by Gram-negative bacteria. In this study, the esterase A (EstA) autotransporter of the rice root-colonizing beneficial bacterium Pseudomonas stutzeri A15 was characterized. A multiple sequence alignment identified EstA as belonging to clade II of the GDSL esterase family. Autologous overexpression allowed the investigation of several features of both autotransporter proteins and GDSL esterases. First, the correctly folded autotransporter was shown to be present in the membrane fraction. Unexpectedly, after separation of the membrane fraction, EstA was detected in the N-laurylsarcosine soluble fraction. However, evidence is presented for the surface exposure of EstA based on fluorescent labeling with EstA specific antibodies. Another remarkable feature is the occurrence of a C-terminal leucine residue instead of the canonical phenylalanine or tryptophan residue. Replacement of this residue with a phenylalanine residue reduced the stability of the β-barrel. Regarding the esterase passenger domain, we show the importance of the catalytic triad residues, with the serine and histidine residues being more critical than the aspartate residue. Furthermore, the growth of an estA-negative mutant was not impaired and cell mobility was not disabled compared to the wild type. No specific phenotype was detected for an estA-negative mutant. Overall, P. stutzeri A15 EstA is a new candidate for the surface display of proteins in environmentally relevant biotechnological applications.