Primary structure of major outer membrane protein I of Escherichia coli B/r

The amino acid sequence of the pore-forming outer membrane protein I (porin) from Escherichia coli B/r has been determined. The polypeptide contains 340 amino acid residues resulting in a molecular weight of 37,205. The transmembrane polypeptide has no stretches of nonpolar residues, uninterrupted by charged side chains, longer than 11 amino acid residues. Regarding polarity, the chain can be subdivided into three regions: a distinctly hydrophilic region between residues 1 and 82 (51.2% polarity), a fairly nonpolar region between residues 83 and 194 (33.9% polarity), and a more hydrophilic region up to the COOH terminus (48% polarity). These results are interpreted as evidence against a simple transmembrane structure in which the membrane is spanned by a single contiguous sequence of hydrophobic amino acids, as has been proposed, for example, for glycophorin.

Pyrolysis of Subbituminous New Mexico Coal

Introduction

Most previous studies on devolatilization have concentrated on the effects of temperature, heating rates, and pressure. Various correlations have resulted from these studies. However, the role of particle size in the devolatilization step has not been studied thoroughly. Since a larger particle size tends to slow down heat and mass-transfer rates, the overall reaction rate will be reduced and the quality and quantity of the product gas will be affected. This study is a preliminary investigation of single-particle devolatilization using 2.5-cm diameter San Juan subbituminous coal. The apparent devolatilization-rate constant and activation energy were determined by a least-squares fit of the initial rate data. Two distinct mathematical models are presented and used to investigate the particle-temperature curve and the weight-loss history. This equipment and system are described in further detail by Stoddart.

Description of Equipment

Our experimental work centered around a bench-scale single-particle reactor, whose internal conditions could be both controlled and monitored by a minicomputer. Supporting equipment included a carrier gas flow system and product collection and analysis systems.

JPT

Evidence for hemiacetal formation between N-acyl-L-phenylalaninals and alpha-chymotrypsin by cross-saturation nuclear magnetic resonance spectroscopy

N-Acetyl-L-phenylalaninal exists predominantly in its hydrated form in aqueous solution, but the aldehyde and not the hydrate is shown by nuclear magnetic resonance (NMR) spectroscopy to be the effective inhibitor of alpha-chymotrypsin. NMR spectroscopy also indicates that the initial alpha-chymotrypsin-N-acetyl-L-phenylalaninal complex is in equilibrium with a hemiacetal formed between the aldehyde and the active site serine residue. The rate of the latter equilibration is slow on the NMR time scale but the hemiacetal can be detected by cross-saturation NMR spectroscopy. N-Benzoyl-L-phenylalaninal is a more potent inhibitor of alpha-chymotrypsin than the N-acetyl derivative and both the formation of the enzyme-inhibitor complex and the hemiacetal are slow on the NMR time scale, but the hemiacetal in the enzyme can be detected by cross-saturation NMR spectroscopy. The N-acyl-L-phenylalaninals also bind to N-methylhistidinyl-57-alpha-chymotrypsin, but clear evidence for hemiacetal formation was not obtained by cross-saturation NMR spectroscopy either because the hemiacetal was not formed or more probably because the rate of dissociation was slow compared with the rate of relaxation of the hemiacetal proton. The dissociation constant of N-benzoyl-L-phenylalaninal to dehydroalaninyl-195-alpha-chymotrypsin was found to be high relative to the dissociation constant to native alpha-chymotrypsin, supporting the NMR evidence that a hemiacetal with the Ser-195 is formed on association of N-benzoyl-L-phenylalaninal with alpha-chymotrypsin.

Major proteins of the Escherichia coli outer cell envelope membrane. Sequence of the cyanogen bromide fragments of protein I from Escherichia coli B/r

The sequence of the cyanogen bromide fragments of one of the major outer membrane proteins of E. coli B/r has been established with the aim of elucidating the primary structure of this protein. Separation of all fragments on one molecular sieve column was achieved upon citraconylation of these fragments. Overlapping peptides were obtained by digestion of the protein, or a cyanogen bromide fragment arising from incomplete cleavage, with trypsin or Staphylococcus aureus protease.

Comparisons of atomic thermal motions for graphite at 300 K based on X-ray, neutron, and phonon-spectrum data

The mean-square amplitudes of vibration in graphite based on an X-ray charge-density analysis are 0.0032 (2) and 0.0140 (3) Å2 parallel to and perpendicular to the basal plane, respectively. Values for the parallel vibrations of 0.0031 (6) and 0.0032 Å2 were derived from temperature-dependent neutron measurements and a calculated phonon spectrum. The neutron measurements and the phonon spectrum both predict lower values [0.0090 (20) and 0.0098 Å2] for the out-of-plane vibrations. This small discrepancy may be caused by small changes in the core atomic scattering factors from the free-atom values or by a deficiency in the phonon-spectrum model.

Major proteins of the outer cell envelope membrane of Escherichia coli K12: multiple species of protein I differ in primary structure

Protein I, one of the major outer membrane proteins of E. coli in most K12 strains is represented by two very similar polypeptides Ia and Ib. Sequential mutations (involving selections for phage resistance) can lead to loss of proteins Ia and Ib. Among "revertants" of such Ia-Ib- mutants clones exist that instead of Ia or Ib produce a third species of protein I, polypeptide Ic. Ichihara and Mizushima [J. Biochem. 83, 1095--1100 (1978)] have shown that proteins Ia and Ib exhibit differences in primary structure. Here evidence is presented indicating that protein Ic also is not identical in primary structure with Ia or Ib. Thus, 3 very similar structural genes appear to exist for the protein I species known to date, and that for Ic normally is silent. Introduction of a functional Ic locus into a Ia+ Ib+ strain caused expression of all three proteins with a reduced rate of synthesis of protein Ia.

Isopeptide linkage between N-alpha-monomethylalanine and lysine in ribosomal protein S11 from Escherichia coli

Protein S11 from the Escherichia coli ribosome has a unique NH2-terminal structure not previously observed among ribosomal proteins. Owing to the formation of an isopeptide bond between a secondary amino acid (N-alpha-monomethylalanine) and the epsilon-amino group of the NH2-terminal lysine residue, a "branching point" is formed. Therefore, two amino acids are seen when the NH2 terminus of the protein is determined.

Sequence determination of protein S9 from the Escherichia coli ribosome

The complete amino acid sequence of ribosomal protein S9 of Escherichia coli has been established. The protein was digested with trypsin and Staphylococcus aureus protease and the resulting peptides were separated by ion exchange chromatography on a new Dowex 50W-X7 microcolumn or a small phosphocellulose column. If necessary, they were rechromatographed on purified cellulose thin-layer plates on a preparative scale. The sequences of the peptides were determined by the micro dansyl-Edman technique, whereas the alignments of the tryptic peptides were mainly established from large cyanogen bromide fragments which were sequenced by the automatic Edman degradation process. Protein S9 is 128 amino acids long and has the following composition: Asx7, Thr5, Ser7, Glx16, Pro3, Gly13, Ala10, Val10, Met3, Ile7, Leu9, Tyr5, Phe4, His1, Lys10, Arg18. The molecular weight as calculated from the amino acid composition is 14 569. A total of 92.6 mg of the lyophilized protein was used for the determination of the primary structure of S9. Most of the material was needed to isolate sufficient amounts of the CNBr-fragments for the automatic degradation in the sequenator.

Influenza immunization: serologic and clinical responses in military units

Two inactivated influenza-virus vaccines were tested and compared in three army training units in Israel. The serological responses to the vaccines and the side-effects were assessed. The vaccines contained the influenza strains which were prevalent in 1974: A2/Port Chalmers/1/73 and B/Hong Kong/8/73. One of the vaccines also contained A2/England/42/72. Both vaccines caused a more than three-fold rise in geometric mean titers against influenza A strains, and about a twofold rise in geometric mean titers against influenza B/Hong Kong/5/73. Approximately 75%-80% of the vaccinees acquired protective hemagglutination-inhibition antibody titers against influenza A strains, while less than 30% acquired protective titers against B strains. In general, there were no significant differences between the serological responses to the two vaccines. More than 50% of the vaccinees experienced at least one systemic side-effect (50.3% with one vaccine and 61.0% with the other). The average number of side-effects per person was between 1.78 and 2.11. However, these side-effects were generally of short duration and caused minimal disability. On the whole, the two vaccines did not differ significantly with regard to the side-effects they caused.

The sequence determination of a protein in a micro scale: the sequence analysis of ribosomal protein L34 of Escherichia coli

The complete amino acid sequence of ribosomal protein L34 has been established by improved micro techniques with 3 mg of the lyophilized protein. The protein was digested with trypsin, thermolysin and chymotrypsin and the resulting peptides were isolated from fingerprints performed on cellulose thin-layer plates. The amino acid sequences of the peptides were determined by the combined micro dansyl-Edman technique using 5 - 10 nmol per sample. Aspartic acid and glutamic acid were distinguished from their amides by use of the color reaction of ninhydrin with the respective amino acid phenylthiohydantoins.

[Epidemiological findings in the study of congenital malformations]

Experience with thalidomide and German measles contracted during pregnancy has focused attention on the question of birth defects. It is suggested that good reasons exist for the carrying out epidemiological investigations to establish the true incidence and geographical and social distribution of such deformities, and hence their possibly "environmental" origin at least in some instances. Such investigations would supplement research into experimental teratology. The advantages, disadvantages and limitations of retrospective and prospective investigations are discussed. A detailed account is given of a prospective survey in progress in Israel. Reference is also made to a similar survey being launched in some Italian cities with the aid of the CNR.