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The vibrational spectrum of ZrF₄ in the gas phase was measured by high-temperature infrared spectroscopy. The spectrum showed two strong bands which were assigned to the asymmetric stretching wavenumber

The unusual base composition of the genome of the human malaria parasite Plasmodium falciparum prompted us to systematically investigate the occurrence of homopolymeric DNA tracts in the P. falciparum genome and, for comparison, in the genomes of Homo sapiens , Saccharomyces cerevisiae , Caenorhabditis elegans , Arabidopsis thaliana , Escherichia coli and Mycobacterium tuberculosis. Comparison of theobserved frequencies with the frequencies as expected for random DNA revealed that homopolymeric (dA:dT) tracts occur well above chance in the eukaryotic genome. In the majority of these genomes, (dA:dT) tract overrepresentation proved to be an exponential function of the tract length. (dG:dC) tract overrepresentation was absent or less pronounced in both prokaryotic and eukaryotic genomes. On the basis of our results, we propose that homopolymeric (dA:dT) tracts are expanded via replication slippage. This slippage-mediated expansion does not operate on tracts with lengths below a critical threshold of 7-10 bp.

Bacteriophage M13 replicative form (RF) DNA was used to direct coupled transcription and translation in cell-free extracts prepared from Escherichia coli. By using RF DNA, isolated from cells infected with appropriate amber mutants of this phage, it has been possible to identify the products of genes I through IV. By using the same methods no gene-product relationship could be demonstrated for genes VI and VII. Coupled in vitro protein synthesis studies on RF-III DNA, a linear double-stranded DNA molecule, obtained after cleavage of either RF-I or RF-II DNA with the restriction endonuclease R.Hin11 from Haemophilus influenzae, indicated that the cleavage site for this enzyme is located in gene II. The in vitro products of both gene III and gene VIII are about 30 and six amino acids longer, respectively, than their native counterparts present within the virion. These results suggest that the latter proteins arise in vivo by cleavage of precursor molecules. Coupled transcription and translation studies on a DNA fragment which only contained the genetic information coding for gene IV protein, obtained after cleavage of RF DNA with the restriction endonuclease R.Hap11 from Haemophilus aphirophilus, indicated that a large number of the in vitro synthesized polypeptides are the result of premature chain termination.

Clo DF13 plasmid deoxyribonucleic acid (DNA) was used as a template to direct transcription and translation in a DNA-dependent cell-free system prepared from Escherichia coli. Analysis of the invitro products on sodium dodecylsulfate-polyacrylamide gels revealed that Clo DF13 DNA directs the synthesis of at least 10 polypeptides ranging in molecular weight from approximately 7,000 to 70,000. Two of these polypeptides could be identified, with respect to their physiochemical and biological characteristics, as the products of the Clo DF13 genes coding for cloacin DF13 and Clo DF13 immunity protein. These results confirm previous findings, obtained which Clo DF13-harbouring minicells of E. coli, that the structural tenes for the latter proteins residue on the Clo DF13 genome.

The standard molar enthalpy of formation of Ba₃B₂O₆(s) has been derived from its enthalpy of solution in HCl(aq). The value Δ_fH^o_m(298.15 K) = -(2344.2±5.8) kJ·mol^-1 has been derived, which is significantly less negative than the value reported previously (Asano, M.; Kou, T. J. Chem. Thermodynamics 1989, 21, 837). Enthalpy increments of the same compound have been measured by drop calorimetry and can be represented by: {H^o_m(T)-H^o_m(298.15 K)}/(J·mol^-1) = 210.8523(T/K) + 42.5254·10^-3 (T/K)² + 1.88436·10⁶ (T/K)^-1 - 72966.1. Copyright 1993, 1999 Academic Press

Escherichia coli minicells harboring plasmid CloDF13 synthesized at least 25 messenger ribonucleic acid (RNA) species; three of these RNAs, a 2,400-, a 2,200-, and a 100-nucleotide RNA, were synthesized in relatively large amounts. Using insertion and deletion mutants of CloDF13 as well as an RNA blotting technique, we could demonstrate that these three RNAs are transcripts from the CloDF13 DNA region from 0 to 40%. This region contains the cloacin and immunity genes and the genetic information involved in plasmid DNA replication. A transcription map of this region is presented and discussed. The data indicate that the cloacin and immunity genes were coordinately transcribed into messenger RNAs of about 2,400 and 2,200 nucleotides, which differ in length at their 3' terminus. RNA polymerase binding studies and in vitro transcription assays indicated that transcription of these genes initiates at a promoter located around 32% on the CloDF13 map. Furthermore, it is shown that a 100-nucleotide RNA is encoded by the CloDF13 DNA region between 7.7 and 8.8% on the plasmid genome; the synthesis of this RNA proceeds in a direction opposite to the transcription of the cloacin and immunity genes.

The solution structure of mutant Tyr41→His of the single-stranded DNA binding protein encoded by gene V of the filamentous bacteriophage M13 has been investigated by nuclear magnetic resonance spectroscopy. Two- and three-dimensional NMR experiments have been employed with a variety of NMR samples of gene V protein, some of which were uniformly enriched with either ¹⁵N or ¹³C. The structure of mutant Tyr41→His of the M13 gene V protein which occurs in solution as a symmetric dimer was calculated using a two-stage procedure. The first step of the procedure involved the calculation of a set of individual monomer structures using the distance geometry program DIANA. This was then followed by the calculation of dimer structures employing "simulated annealing" protocols with the program X-PLOR. Hereby, the problem of assignment of intra- and inter-subunit NOEs of the symmetric dimer was circumvented through use of a target function that correctly deals with the intra- and inter-subunit contributions to the NOE peaks. Furthermore, a pseudo energy term was employed to restrain the symmetry of the dimer. In addition to this novel calculation strategy, we have incorporated distance information for a set of NOEs which were unambiguously identified as inter-subunit NOEs using an NMR strategy based on asymmetric labelling. A total of 20 structures were calculated for the M13 gene V protein mutant Tyr41→His based on approximately 1000 experimental restraints derived from the NMR data. The structure of residues 1 to 15 and 29 to 87 of both monomers is reasonably well determined with an average atomic r.m.s. difference between the individual structures and the respective mean structure of ≈ 0·9 Å for the backbone atoms and ≈ 1·4 Å for all atoms. The orientation of the exposed anti-parallel β-loop (residues 16 to 28) with respect to the core could not be determined. The molecular architecture of each of the monomers includes a five-stranded β-barrel enclosing a hydrophobic core and two-antiparallel β-loops. The dimer structure is stabilized predominantly by hydrophobic residues primarily involving the symmetry-related dyad domains (residues 64 to 82) of the monomers. Residues which are close to bound single-stranded DNA were identified previously from binding experiments with spin-labelled oligonucleotides. The solution structure of mutant Tyr41→His of the M13 gene V proteins is consistent with these binding data and provides a clear view of the protein's single-stranded DNA binding path. Copyright 1994, 1999 Academic Press

A contact analysis and a series of restrained molecular dynamics simulations were employed to derive a model of the complex between single-stranded DNA and the single-stranded DNA-binding protein encoded by gene V of the filamentous phage M13. The study is based on the recently elucidated solution structure of the Tyr41→His mutant of the protein. Electron microscopy studies, indicating that the complex forms a flexible, left-handed helical coil with a diameter of 8 to 9 nm and an average pitch of 9 nm, were taken into consideration. The contact analysis served to determine the helix parameters that permit the energetically most favourable packing of protein molecules. Then a protein super-helix was built, into which two extended strands of DNA were modelled using restrained molecular dynamics. Specific constraints were included to ensure that the DNA would position itself into the binding groove of the protein. These constraints are based on recent NMR spin label experiments which offered a direct identification of the amino acids of the protein present in the DNA-binding domain. We present a model for the complex which is in full agreement with the existing reliable biophysical and biochemical data. A description of the protein-protein interface is given and the protein-DNA interaction is discussed in view of the derived model. In addition, we demonstrate that, on the basis of the available experimental data, and not imposing the left-handedness of the nucleoprotein complex, it is feasible to build also a plausible model for the complex which exhibits the opposite, i.e. right-handed, helical sense. This nucleoprotein structure features characteristics highly similar to those of the left-handed helix. Copyright 1994, 1999 Academic Press

In vitro transcription and coupled transcription-translation studies have been performed with restriction fragments of bacteriophage M13 replicative-form DNA which contain either gene III, gene VI, or gene I. It could be demonstrated that DNA fragments which contain gene III were able to direct the synthesis of gene III protein. Fragments which encompassed genes VI and I gave rise to the synthesis of gene I protein only, whereas gene I-containing fragments were able to direct the synthesis of gene I protein. None of the fragments studied gave rise to a detectable level of gene VI protein, although an RNA transcript of gene VI could readily be obtained during in vitro transcription of the relevant gene VI-containing DNA fragments. From these results we have concluded that the promoters A0.44 and A0.49 are located in front of genes VI and I, respectively, and that gene III is also equipped with a promoter (X0.25). Introduction of a single cleavage within the gene III region does not abolish the expression of genes VI and I in vitro. Hence, the expression of these genes is not solely dependent on the initiation of RNA synthesis at the gene III promoter or on leakage of transcription through the central termination site (T0.25), but is also determined by the initiation frequency of RNA synthesis at their individual promoters.

Abstract: Ammonium feldspar was grown hydrothermally from a gel, having a stchiometric Al2O36SiO2 composition. As a source for NH 4+ , a 25 percent NH3 solution was used. Internal Cr/CrN and graphite/methane buffers fixed the fugacity of NH3 during the experiments. Unit cell parameters of the synthetic ammonium feldspar are a: 0.8824 (5) nm, b: 1.3077 (8) nm, c: 0.7186 (4) nm, β: 116.068 (12), V: 0.7448 (34) nm3. the X-ray power diffraction pattern is measured and indexed in accordance to the space group C2/m. Infrared and thermal gravimetric analyses provide no evidence for the presence of structurally bound water molecules in the crystal structure of synthetic ammonium feldspar. Hydrothermally grown anhydrous ammonium feldspar is shown to be identical to the mineral buddingtonite by the similarity of the data between the synthetic and natural materials. There may be justification for considering natural buddingtonite as an anhydrous feldspar with the ideal formula NH4Si3O8. Reexamination of natural specimens is desirable.

The minor capsid proteins C and D from phage M13 have been characterized by differential amino acid labeling and amino-terminal sequence analysis. We demonstrate that D protein (Mr 12,260) is the product of gene VI, whereas the C component is composed of the products of both gene VII (Mr 3580) and gene IX (Mr 3650). Our data further show that the proteins of genes VI, VII, and IX are not subject to proteolytic processing but are packaged into mature virions as their primary translational products. On the basis of incorporation of specific amino acids, the copy numbers of these proteins in M13 virions could be estimated relative to the number of A protein molecules. The M13 phage contains on the average 5 molecules of A protein, 5 molecules of VI protein and 3-4 molecules of both VII protein and IX protein. These copy numbers remained unchanged in M13 recombinant phages of up to two times the length of wild-type phages, a fact that indicates that these minor capsid proteins are located at either one or both ends of the phage filament.

The circular, single-stranded DNA genome of the Pf3 bacteriophage was sequenced in its entirety by each of two methods, the M13-dideoxy chain termination method and the chemical degradation method. It consists of 5,833 nucleotides. With respect to both the DNA and the protein sequences, there is virtually no homology between Pf3 and the phages Ff (M13, f1, and fd) and IKe. However, similarities between these phages were noted with respect to their overall genome organizations. The gene for the single-stranded DNA-binding protein is followed by the gene for the major coat protein and then by a transcription termination signal. Open reading frames for seven other proteins were predicted, and their sizes and order show a fair correspondence to the sizes and order of the genes of the Ff phages and IKe. In addition, several regions have the potential to form stem and loop structures similar to those in the intergenic region of the Ff phage genome, but in Pf3 some are within open reading frames. Evolutionary relationships between Pf3 and the Ff phages and IKe are thus apparent through the correspondence of overall gene order rather than through primary sequence homologies.

The standard molar enthalpy of solution of In(OH)3in HCl(aq) of concentration 9.33 mol·dm−3has been measured. Combining this value with auxiliary values, the standard molar enthalpy of formation has been derived: ΔfHm°{In(OH)3, s, 298.15 K} = −(927.6 ± 0.5) kJ·mol−1.