Search PubMed⌕ Search

Biomedical subjects

V Jonas

Publications and source records attributed to V Jonas.

17 recordsLinked to original sources
PubMed2001

Superelectrophilic tetrakis(carbonyl)palladium(II)- and -platinum(II) undecafluorodiantimonate(V), [Pd(CO)4][Sb(2)F(11)]2 and [Pt(CO)4][Sb(2)F(11)]2: syntheses, physical and spectroscopic properties, their crystal, molecular, and extended structures, and density functional calculations: an experimental, computational, and comparative study .

The salts [M(CO)(4)][Sb(2)F(11)](2), M = Pd, Pt, are prepared by reductive carbonylation of Pd[Pd(SO(3)F)(6)], Pt(SO(3)F)(4) or PtF(6) in liquid SbF(5), or HF-SbF(5). The resulting moisture-sensitive, colorless solids are thermally stable up to 140 degrees C (M = Pd) or 200 degrees C (M = Pt). Their thermal decompositions are studied by differential scanning calorimetry (DSC). Single crystals of both salts are suitable for an X-ray diffraction study at 180 K. Both isostructural salts crystallize in the monoclinic space group P2(1)/c (No. 14). The unit cell volume of [Pt(CO)(4)][Sb(2)F(11)](2) is smaller than that of [Pd(CO)(4)][Sb(2)F(11)](2) by about 0.4%. The cations [M(CO)(4)](2+), M = Pd, Pt, are square planar with only very slight angular and out-of-plane deviations from D(4)(h)() symmetry. The interatomic distances and bond angles for both cations are essentially identical. The [Sb(2)F(11)](-) anions in [M(CO)(4)][Sb(2)F(11)](2,) M = Pd, Pt, are not symmetry-related, and both pairs differ in their Sb-F-Sb bridge angles and their dihedral angles. There are in each salt four to five secondary interionic C- -F contacts per CO group. Of these, two contacts per CO group are significantly shorter than the sum of the van der Waals radii by 0.58 - 0.37 A. In addition, structural, and spectroscopic details of recently synthesized [Rh(CO)(4)][Al(2)Cl(7)] are reported. The cations [Rh(CO)(4)](+) and [M(CO)(4)](2+), M = Pd, Pt, are characterized by IR and Raman spectroscopy. Of the 16 vibrational modes (13 observable, 3 inactive) 10 (Pd, Pt) or 9 (Rh), respectively, are found experimentally. The vibrational assignments are supported by DFT calculations, which provide in addition to band positions also intensities of IR bands and Raman signals as well as internal force constants for the cations. (13)C NMR measurements complete the characterization of the square planar metal carbonyl cations. The extensive characterization of [M(CO)(4)][Sb(2)F(11)](2), M = Pd, Pt, reported here, allows a comparison to linear and octahedral [M(CO)(n)()][Sb(2)F(11)](2) salts [M = Hg (n = 2); Fe, Ru, Os (n = 6)] and their derivatives, which permit a deeper understanding of M-CO bonding in the solid state for superelectrophilic cations with [Sb(2)F(11)](-) or [SbF(6)](-) as anions.

Journal Article↗
PubMed2000

Syntheses, molecular structures, and vibrational spectra of chloropentacarbonylrhodium(III) and -iridium(III) undecafluorodiantimonate(V), [Rh(CO)5Cl][Sb2F11]2 and [Ir(CO)5Cl][Sb2F11]2: an experimental and density functional study.

The reactions of either bis(mu-chloro)tetracarbonyldirhodium(I), [Rh(CO)2(mu-Cl)]2, or chlorotricarbonyliridium(I), [Ir(CO)3Cl]n, in the conjugate Brønsted-Lewis superacid HF-SbF5 and in a CO atmosphere, produce [Rh(CO)5Cl][Sb2F11]2 or [Ir(CO)5Cl][Sb2F11]2, respectively. In these oxidative carbonylation reactions, antimony(V) fluoride functions as an oxidizing agent. The reduced product is identified as 6SbF3.5SbF5. [Rh(CO)5Cl][Sb2F11]2 is obtained in the form of single crystals. Crystal data: monoclinic, space group P2(1) (No. 4); a = 9.721(1), b = 12.602(1), c = 10.538(1) A; beta = 106.51(1) degrees; V = 1237.7(2) A3; Z = 2; T = 300 K; R1 [I > 3 sigma (I)] = 0.0367, wR2 = 0.0739. Single crystals of [Ir(CO)5Cl][Sb2F11]2 are produced in small amounts from a solution of mer-Ir(CO)3(SO3F)3 in magic acid, HSO3F-SbF5. The possible source of chlorine will be discussed. Crystal data for [Ir-(CO)5Cl][Sb2F11]2: monoclinic, space group P2(1) (No. 4); a = 9.686(2), b = 12.585(2), c = 10.499(2) A; beta = 106.59(2) degrees; V = 1226.5(4) A3; Z = 2; T = 294 K; R1[I > 3 sigma (I)] = 0.032, Rw = 0.031. The bond lengths and bond angles are nearly identical in the two isostructural salts; however, the cell volume of [Ir(CO)5Cl][Sb2F11]2 is slightly smaller than that of [Rh(CO)5Cl][Sb2F11]2. The cations (point group C4v) feature unusually long M-C bonds (M = Rh, Ir) and correspondingly short CO bonds, as well as high CO stretching wavenumbers and high CO stretching force constants. The [Sb2F11]- anions are not symmetry related, and their dihedral and bridge angles differ slightly in both salts. There are significant interionic contacts in [Ir(CO)5Cl][Sb2F11]2 exclusively of the C-F type (about 2 for each C atom of the five carbonyl groups) resulting in extended structures. The vibrational spectra for both [M(CO)5Cl]2+ cations (M = Rh, Ir) are assigned with the help of density functional calculations, which also provide intensities for IR and Raman bands. While [Rh(CO)5Cl]2+ is the first cationic carbonyl derivative of Rh(III), the vibrational and structural parameters for [Ir(CO)5Cl]2+ are compared to data for [Ir(CO)6]3+ and mer-Ir(CO)3(SO3F)3.

Journal Article↗
PubMed2000

The role of clinical suspicion in evaluating a new diagnostic test for active tuberculosis: results of a multicenter prospective trial.

CONTEXT: In laboratory trials, nucleic acid amplification tests for the diagnosis of tuberculosis (TB) are more accurate than acid-fast bacilli (AFB) smear microscopy and are faster than culture. The impact of these tests on clinical diagnosis is not known. OBJECTIVE: To assess the performance of a nucleic acid amplification test, the enhanced Mycobacterium tuberculosis Direct (E-MTD) test, against a uniform clinical standard stratified by level of clinical suspicion. DESIGN: Prospective multicenter trial conducted between February and December 1996, documenting the clinical suspicion of TB at enrollment and using final comprehensive diagnosis as the criterion standard. SETTING: Six urban medical centers and 1 public health TB clinic. PATIENTS: A total of 338 patients with symptoms and signs consistent with active pulmonary TB and complete clinical diagnosis were stratified by the clinical investigators to be at low (< or =25%), intermediate (26%-75%), or high (>75%) relative risk of having TB. MAIN OUTCOME MEASURES: Sensitivity, specificity, and positive and negative predictive values of the E-MTD test in clinical suspicion of groups with low (n = 224); intermediate (n = 68); and high (n = 46) clinical suspicion of TB. RESULTS: Based on comprehensive clinical diagnosis, sensitivity of the E-MTD test was 83%, 75%, and 87% for low, intermediate, and high clinical suspicion of TB, respectively, and corresponding specificity was 97%, 100%, and 100% (P = .25). Positive predictive value of the E-MTD test was 59% (low), 100% (intermediate), and 100% (high) compared with 36% (low), 30% (intermediate), and 94% (high) for AFB smear. Corresponding negative predictive values were 99%, 91%, and 55% [corrected] (E-MTD test) vs 96%, 71%, and 37% (AFB smear). CONCLUSIONS: For complex diagnostic problems like TB, clinical risk assessments can provide important information regarding predictive values more likely to be experienced in clinical practice. For this series, a clinical suspicion of TB was helpful in targeting areas of the clinical spectrum in which nucleic acid amplification tests can make an important contribution.

Adult↗
PubMed2000

The Tetrakis(carbonyl)dioxoosmium(VI) Cation: trans-

The first carbonyl compound of a transition metal in the oxidation state +6 was obtained by reductive carbonylation of OsO(4) in SbF(5). Through the use of extensive IR, NMR, and UV/Vis spectroscopic studies as well as density functional calculations it was determined that the trans-[OsO(2)(CO)(4)](2+) cation adopts the octahedral structure shown in the picture with trans oxygen atoms.

Journal Article↗
PubMed2000

False-positive results for Mycobacterium celatum with the AccuProbe Mycobacterium tuberculosis complex assay.

Mycobacterium celatum type 1 was found to cross-react in the AccuProbe Mycobacterium tuberculosis complex assay. Subsequently, we found a statistically significant increase in the relative light units with lower temperatures, suggesting that it is necessary to perform this AccuProbe assay at between 60 and 61 degrees C. We also recommend the inclusion of M. celatum type 1 as a negative control.

DNA Probes↗
PubMed1997

Detection of Mycobacterium tuberculosis by molecular methods.

A review of the current literature regarding performance of the polymerase chain reaction and transcription mediated amplification with respect to diagnosis of tuberculosis is presented. Additional studies of the usefulness of these methods for predicting the efficacy of treatment by amplification of rRNA and DNA are also discussed. Application of the methodologies to nonrespiratory specimens for diagnosis of tuberculosis are presented.

Chromatography, High Pressure Liquid↗
PubMed1996

Semantide- and chemotaxonomy-based analyses of some problematic phenotypic clusters of slowly growing mycobacteria, a cooperative study of the International Working Group on Mycobacterial Taxonomy.

During previous cooperative numerical taxonomic studies of slowly growing mycobacteria, the International Working Group on Mycobacterial Taxonomy described a number of strains whose taxonomic status was ambiguous. A new study of DNA, RNA, and proteins from 66 of these organisms was performed to correlate their properties with phenotypic clustering behavior; the results of this study permitted 51 of the strains studied to be assigned to known species. The methods used to characterize the semantides included nucleotide sequencing and assessment of levels of semantide relatedness by affinity binding techniques, including whole DNA-DNA hybridization, probe hybridization, and antibody binding. There was good overall agreement between the phenotypic and chemotaxonomic clusters and the groups of organisms identified by semantide analyses. Our results supported the conclusion that we should continue to rely on polyphasic taxonomy to provide satisfactory systematic resolution of members of the genus Mycobacterium. We identified no single 16S rRNA interstrain nucleotide sequence difference value that unequivocally defined species boundaries. DNA-DNA hybridization remains the gold standard, but common resources are needed to permit DNA-DNA hybridization analyses to be made available to laboratories that are not prepared to use this technology. One of the large novel clusters which we studied corresponds to the recently described species Mycobacterium interjectum, a pathogen that resembles the nonpathogen Mycobacterium gordonae phenotypically. We also identified strains that appear to represent ribovars of Mycobacterium intracellulare which do not react with the commercial diagnostic probes that are currently used for identification of this species. Other branches or clusters consisted of too few strains to permit a decision about their taxonomic status to be made.

Bacterial Proteins↗
PubMed1996

Amplification of rRNA for assessment of treatment response of pulmonary tuberculosis patients during antimicrobial therapy.

The time course of persistence of Mycobacterium tuberculosis as measured by detection of rRNA, acid-fast bacillus (AFB) smear, and culture was determined for pulmonary tuberculosis patients during antimicrobial therapy. Twenty-three patients who were initially AFB smear positive and who subsequently completed a course of antimicrobial therapy were selected for the study. Sequential specimens were tested by AFB smear, culture, and rRNA amplification (Gen-Probe Amplified Mycobacterium Tuberculosis Direct Test [MTD]). The initial diagnostic specimens of all patients were positive by culture; those of 22 patients (96%) also were positive by MTD. Overall, MTD results remained positive longer than both smear and culture results. The median times to the last positive test result were 9 days for AFB smear, 26 days for culture, and 30 days for MTD. The last positive test result was the AFB smear result in 4% of cases, the culture result in 22%, and the MTD result in 52%. Fifty-six percent of patients had a period of shedding of noncultivable M. tuberculosis which was detected by MTD after culture results had converted to negative. This noncultivable period lasted 7 to 245 days. All three tests became reproducibly negative before the end of therapy and remained negative during follow-up for up to 1 year. These results indicate that during successful antimicrobial therapy, M. tuberculosis is eliminated in sputum samples as measured by amplification of rRNA, as well as by AFB smear and culture. No long-term rRNA carrier state was detected. While the time course of clearance of M. tuberculosis measured by rRNA overall was longer than with the two traditional tests, the rRNA test results allow sensitive and precise measurement of the clearance of noncultivable M. tuberculosis from respiratory specimens. This attribute may allow rRNA testing to be useful in clarifying patient response to antimicrobial therapy.

Adult↗
PubMed1995

Performance of the Gen-Probe amplified Mycobacterium tuberculosis direct test in a laboratory that infrequently isolates Mycobacterium tuberculosis.

The performance of the Gen-Probe Mycobacterium tuberculosis direct (MTD) test was assessed in a laboratory whose specimens were derived from a population with a low prevalence (1.3%) of tuberculosis. A total of 339 specimens from 113 patients were included in the study. Nine of 10 MTD positive samples were culture positive (smear positive, n = 7; smear negative, n = 1; smear not ordered, n = 2). The 10th MTD-positive sample, which was smear and culture negative, was from a patient whose two other study specimens were smear and culture positive and who had a clinical history consistent with tuberculosis. Prior to and following resolution of discrepant results, the sensitivities and specificities of the MTD test relative to culture were 100 and 99.7% and 100 and 100%, respectively.

Bacteriological Techniques↗
PubMed1993

Detection and identification of Mycobacterium tuberculosis directly from sputum sediments by amplification of rRNA.

Seven hundred fifty-eight processed sputum sediments received for the diagnosis of tuberculosis or other mycobacterial infections were tested by utilizing a rRNA target amplification assay and traditional culture techniques. The results from the rRNA target amplification assay (Gen-Probe Amplified Mycobacterium Tuberculosis Direct Test), available in 5 h, were compared with the results from standard culture techniques held for 6 weeks. A total of 119 specimens (16%) were culture positive for Mycobacterium tuberculosis. Overall sensitivity, specificity, positive predictive value, and negative predictive value were 82, 99, 97, and 96%, respectively, for the Gen-Probe assay; 88, 100, 100, and 97%, respectively, for culture; and 53, 99.8, 99.6, and 91%, respectively, for fluorochrome stain. The Gen-Probe assay employs the isothermal enzymatic amplification of M. tuberculosis complex rRNA followed by detection of the amplicon with an acridinium ester-labeled DNA probe. This assay has the potential of reducing the time for diagnosis of tuberculosis to 1 day.

Gene Amplification↗
PubMed1985

Alternative RNA processing events in human calcitonin/calcitonin gene-related peptide gene expression.

Two mRNAs generated as a consequence of alternative RNA processing events in expression of the human calcitonin gene encode the protein precursors of either calcitonin or calcitonin gene-related peptide (CGRP). Both calcitonin and CGRP RNAs and their encoded peptide products are expressed in the human pituitary and in medullary thyroid tumors. On the basis of sequence comparison, it is suggested that both the calcitonin and CGRP exons arose from a common primordial sequence, suggesting that duplication and rearrangement events are responsible for the generation of this complex transcription unit.

Base Sequence↗
PubMed1982

Alternative RNA processing in calcitonin gene expression generates mRNAs encoding different polypeptide products.

Alternative processing of RNA transcripts from the calcitonin gene results in the production of distinct mRNAs encoding the hormone calcitonin or a predicted product referred to as calcitonin gene-related peptide (CGRP). The calcitonin mRNA predominates in the thyroid while the CGRP-specific mRNA appears to predominate in the hypothalamus. These observations lead us to propose a model in which developmental regulation of RNA processing is used to increase the diversity of neuroendocrine gene expression.

Animals↗
PubMed1982

Calcitonin COOH-terminal cleavage peptide as a model for identification of novel neuropeptides predicted by recombinant DNA analysis.

A strategy is presented for identification of putative neurohormones that were predicted by sequence analysis of recombinant cDNa molecules. The nucleotide sequence of a cloned calcitonin cDNA insert predicts that the proteolytic excision of calcitonin from a 136-amino acid precursor should generate two additional peptides derived from regions flanking the calcitonin sequence on the NH2 and carboxyl termini. The predicted 16-amino acid COOH-terminal cleavage peptide (NH2-Asp-Met-Ala-Lys-Asp-Leu-Glu-Thr-Asn-His-His-Pro-Thr-Phe-Gly-Asn-COOH) was chemically synthesized using solid phase procedures. Antibodies against this synthetic hexadecapeptide detect immunologically cross-reactive material in tissue extracts from normal thyroid glands and calcitonin-producing medullary thyroid carcinomas. Each of the four calcitonin mRNA-directed cell-free translation products contain the immunological determinants for both calcitonin and the COOH-terminal cleavage peptide.

Amino Acid Sequence↗
PubMed1981

Nucleotide sequence and formation of the transforming gene of a mouse sarcoma virus.

The complete nucleotide sequence of the transforming gene of a mouse sarcoma virus has been determined. It codes for a protein of 374 amino acids. The nucleotide sequence of the junctions between a murine leukaemia virus and cellular sequences leading to the formation of the viral transforming gene have also been elucidated. The viral transforming sequence and its cellular homologue share an uninterrupted stretch of 1,159 nucleotides, with few base substitutions. The predicted amino acid sequence of the mouse sarcoma virus transforming gene was found to share considerable homology with the proposed amino acid sequence of the avian sarcoma virus oncogene (src) product.

Amino Acid Sequence↗