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S B Needleman

Publications and source records attributed to S B Needleman.

28 records · Page 2Linked to original sources
PubMed1969

Homology of Pseudomonas cytochrome c-551 with eukaryotic c-cytochromes.

The homology of Pseudomonas cytochrome c-551 with eukaryotic cytochromes c is examined with a computer-based procedure devised to determine whether similarities exist between these proteins. One method is given by which the more recently evolved cytochromes c might have arisen from the Pseudomonas protein. This procedure involves only common genetic phenomena and accounts for most of the structural differences between the bacterial and mammalian cytochromes. A time-scale relationship between the c-cytochromes from several microorganisms, a mold, yeast, and the eukaryotic organisms is proposed.

Amino Acid Sequence↗
PubMedDate not supplied

Limits of linearity and detection for some drugs of abuse.

The limits of linearity (LOL) and detection (LOD) are important factors in establishing the reliability of an analytical procedure for accurately assaying drug concentrations in urine specimens. Multiple analyses of analyte over an extended range of concentrations provide a measure of the ability of the analytical procedure to correctly identify known quantities of drug in a biofluid matrix. Each of the seven drugs of abuse gives linear analytical responses from concentrations at or near their LOD to concentrations several-fold higher than those generally encountered in the drug screening laboratory. The upper LOL exceeds the Department of Navy (DON) cutoff values by factors of approximately 2 to 160. The LOD varies from 0.4 to 5.0% of the DON cutoff value for each drug. The limit of quantitation (LOQ) is calculated as the LOD + 7 SD. The range for LOL is greater for drugs analyzed with deuterated internal standards compared with those using conventional internal standards. For THC acid, cocaine, PCP, and morphine, LOLs are 8 to 160-fold greater than the defined cutoff concentrations. For the other drugs, the LOL's are only 2 to 4-fold greater than the defined cutoff concentrations.

Gas Chromatography-Mass Spectrometry↗
PubMedDate not supplied

Liquid-liquid extraction systems for THC-COOH and benzoylecgonine.

Because DuPont Instruments has discontinued commercial availability of the PREP automated sample processor, an alternate method for the general extraction of THC-COOH and benzoylecgonine from a urine matrix in the military drug screening laboratories' standard procedure is needed. The liquid-liquid extraction method presented for isolation of THC-COOH uses extraction with isobutanol-hexane followed by back extraction into an aqueous alkaline medium and results in a percent recovery of 104.24 +/- 9.71%. The isolation of benzoylecgonine involves extraction into ethanol-methylene chloride followed by evaporation and derivatization with 1-iodopropane; recovery is 102.43 +/- 3.13%.

Cocaine↗