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M Willert

Publications and source records attributed to M Willert.

5 recordsLinked to original sources
PubMed1998

Comparison of the MB/BacT system with a revised antibiotic supplement kit to the BACTEC 460 system for detection of mycobacteria in clinical specimens.

The MB/BacT system (MB/BacT) with a revised antibiotic supplement kit was compared with the BACTEC 460 system (BACTEC 460) in a test of 488 specimens submitted for mycobacterial culture from 302 patients. Twenty-four Mycobacterium tuberculosis isolates were detected by the BACTEC 460 versus 23 isolates by the MB/BacT. Mean time until detection of M. tuberculosis isolates identified by both systems was 11.9 days for the BACTEC 460 versus 13.7 days for the MB/BacT (P = 0.046). M. avium complex was detected in 12 specimens by the MB/BacT versus 10 specimens by the BACTEC 460. Only 8 of 14 (57%) M. avium isolates were detected by both systems, with a mean time until detection of 10.1 days for the BACTEC 460 and 14.2 days for the MB/BacT (P = 0.009). The BACTEC 460 and the MB/BacT detected M. gordonae in four specimens, but only a single specimen was positive by both systems. One M. fortuitum isolate and one of five M. kansasii isolates were recovered only by the BACTEC 460. The bacterial overgrowth rate was 7.0% for the MB/BacT versus 4.1% for the BACTEC 460. We found the MB/BacT to be comparable to the BACTEC 460 for mycobacterial detection. Even though time until detection with the MB/BacT was slightly longer (1.8 days longer for M. tuberculosis and 4.1 days for M. avium [mean values]) and the bacterial overgrowth rate was somewhat higher, the decreased labor, the availability of a computerized data management system, and the noninvasive, nonradiometric aspects of the MB/BacT offset these relative disadvantages and make it an acceptable alternative for use in the diagnostic laboratory.

Anti-Bacterial Agents↗
PubMed1998

A study of baker's yeast reduction of piperidone-carboxylates.

The stereoselective baker's yeast reduction of various N-protected piperidone-carboxylic acids have been studied, and the enantioselectivity was found to be widely dependent on whether fermenting or non-fermenting conditions were employed. Thus reaction of N-tert-butoxycarbonyl-4-oxopiperidine-3-carboxylic acid ethyl ester (6) with fermenting baker's yeast gave almost racemic N-tert-butoxycarbonyl-4-hydroxypiperidine-3-carboxylic acid ethyl ester (7), however, with complete diastereoselectivity. Reduction of 6 with non-fermenting yeast gave 7 with a 24-41% enantiomeric excess. Similarly, reduction of N-tert-butoxycarbonyl-3-oxopiperidine-4-carboxylic acid ethyl ester (17) with fermenting baker's yeast gave racemic N-tert-butoxycarbonyl-3-hydroxypiperidine-4-carboxylic acid ethyl ester [(+/-)-18] diastereoselectively. A convenient method for determining the enantiomeric excess of the hydroxypiperidine carboxylic acids derivatives was found in the reaction with Sanger's reagent followed by HPLC on a chiral column.

Carboxylic Acids↗
PubMed1990

BacT/Alert: an automated colorimetric microbial detection system.

BacT/Alert (Organon Teknika Corp., Durham, N.C.) is an automated microbial detection system based on the colorimetric detection of CO2 produced by growing microorganisms. Results of an evaluation of the media, sensor, detection system, and detection algorithm indicate that the system reliably grows and detects a wide variety of bacteria and fungi. Results of a limited pilot clinical trial with a prototype research instrument indicate that the system is comparable to the radiometric BACTEC 460 system in its ability to grow and detect microorganisms in blood. On the basis of these initial findings, large-scale clinical trials comparing BacT/Alert with other commercial microbial detection systems appear warranted.

Bacteria↗
PubMedDate not supplied

Fluorescence-quenched solid phase combinatorial libraries in the characterization of cysteine protease substrate specificity.

To map the substrate specificity of cysteine proteases, two combinatorial peptide libraries were synthesized and screened using the archetypal protease, papain. The use of PEGA resin as the solid support for library synthesis facilitated the application of an on-resin fluorescence-quenched assay. Results from the screening of library 2 indicated a preference for Pro or Val in the S3 subsite and hydrophobic residues in S2; the most prevalent residue not being Phe but Val. The S1 subsite exhibited a dual specificity for both small, nonpolar residues, Ala or Gly, as well as larger, Gln, and charged residues, Arg. Small residues predominated in the S1'-S4' subsites. Active peptides from the libraries and variations thereof were resynthesized and their kinetics of hydrolysis by papain assessed in solution phase assays. Generally, there was a good correlation between the extent of substrate cleavage on solid phase and the kcat/KM's obtained in solution phase assays. Several good substrates for papain were obtained, the best substrates being Y(NO2)PMPPLCTSMK(Abz) (kcat/KM = 2109 (mM s)-1), Y(NO2)PYAVQSPQK(Abz) (kcat/KM = 1524 (mM s)-1), and Y(NO2)PVLRQQRSK(Abz) (kcat/KM = 1450 (mM s)-1). These results were interpreted in structural terms by the use of molecular dynamics (MD). These MD calculations indicated two different modes for the binding of substrates in the narrow enzyme cleft.

Amino Acid Sequence↗