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S Ackerman

Publications and source records attributed to S Ackerman.

54 records · Page 3Linked to original sources
PubMed1983

The effect of phenylalanine derivatives on the solubility of deoxyhemoglobin S. A model class of gelation inhibitors.

Among the class of non-covalent inhibitors of deoxyhemoglobin S gelation, the aromatic amino acids have been shown to be the most effective. We have examined several synthetic chemical modifications of phenylalanine in order to determine the stereospecific constraints for inhibition of gelation by this class of compounds. The phenylalanine derivatives with ring modification by electron-donating groups (NH2, CH3, or OH) inhibited gelation to the same order of magnitude as phenylalanine (10-20% increase in deoxyhemoglobin S solubility at 32 mM). The phenylalanine derivative with the electron-withdrawing group NO2 in the p-position behaved similarly, but the inhibitory effect was eliminated by NO2 in the m- and possibly o-positions. Furthermore, side-chain modifications also eliminated the inhibitory effect. These studies, in conjunction with crystallographic analyses of the binding sites of gelation inhibitors, may provide a rational strategy for finding suitable compounds (whether covalent or non-covalent inhibitors) with appropriate physicochemical and biological properties to pursue as potential therapies with sickle cell disease.

Anemia, Sickle Cell↗
PubMed1982

Mechanism of RNA polymerase II--specific initiation of transcription in vitro: ATP requirement and uncapped runoff transcripts.

The ATP analog 5'-adenylyl imidodiphosphate (AMP-PNP) inhibits transcription of specific genes by the RNA polymerase II contained in whole cell extracts, not only with promoters that contain A as the first nucleotide of the transcript, but also with those that initiate transcripts with G or U. The analog AMP-PNP (a competitive inhibitor of ATP) probably acts at the level of initiation of transcription, but it can be used for elongation by RNA polymerase II in isolated nuclei or in the whole cell extract. AMP-PNP and the other imidotriphosphates have little effect on purified HeLa cell RNA polymerase II initiation and elongation of transcription. Since RNA polymerase III in the crude system both initiates and elongates transcripts with AMP-PNP, we conclude that the availability of the beta-gamma bond of ATP is an indispensable requirement for faithful and specific in vitro initiation only by RNA polymerase II in the whole cell extract. Uncapped U- or G-initiated transcripts were obtained in the presence of UMP-PNP or GMP-PNP, the respective imidodiphosphate analogs. The presence of the 5'-terminal imidotriphosphate at the same oligonucleotide as the cap for U-initiated precursors established that transcription initiation and capping occur at the same site. Capping is not required for transcription by RNA polymerase II in the in vitro system. Methylation of the 2' ribose of the initiating nucleotide does not occur on the imidonucleotide containing 5' ends of adenovirus EIV or murine leukemia virus long terminal repeat.

Adenosine Triphosphate↗
PubMed1982

Mechanism of action of dichloro-beta-D-ribofuranosylbenzimidazole: effect on in vitro transcription.

The adenosine analog 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) and its mono- and triphosphate derivatives inhibit RNA polymerase II-specific transcription in an extract of whole HeLa cells. The analog does not inhibit RNA polymerase III-specific adenovirus VA RNA transcription in the whole cell extract. With purified RNA polymerase II under nonspecific transcription conditions, no effect on DRB could be detected. DRB is equally effective in inhibiting in vitro transcription from several of the adenovirus promoters and the human epsilon-globin gene. The inhibitory effects are in the order DRB greater than DRB monophosphate greater than DRB triphosphate. Thus DRB acts in vitro presumably on systems in which specific RNA polymerase II initiation of transcription occurs and with no detectable effect on premature termination. This will provide a suitable model for study of the molecular mechanism of action of DRB on transcription.

Cell-Free System↗
PubMed1979

Enzymic polyadenylation of 5S ribosomal ribonucleic acid and synthesis of a complementary deoxyribonucleic acid.

The 5S ribosomal RNA has been isolated, pure and intact, from rat liver (5 mg of 5S RNA from 150g of liver). The 5S RNA serves as a primer for calf thymus poly(A) polymerase with 20% of the efficiency of (Ap)3A. Bacterial 5S RNA and transfer RNA also serve as primers; rat liver 18S and 28S ribosomal RNAs support poly(A) synthesis poorly. Neither the 5S RNA primer nor the appended poly(A) tract is nicked or degraded by poly(A) polymerase, and initiation of poly(A) tracts on 5S RNA primers continues throughout the reaction period. The rate of initiation is dependent on the enzyme concentration; the ATP concentration affects the rate of elongation. The polyadenylated material increases in size over time, with the largest material reaching a size of 6.8 S in 5 h, corresponding to an appended poly(A) tract of 140 nucleotides. Using polyadenylated 5S RNA, oliog(dTY as primer, and avian myeloblastosis virus reverse transcriptase, we synthesized DNA complementary to 5S RNA. The complementary DNA has an apparent molecular weight (in alkaline sucrose gradients) of 4.3 X 10(4). Base composition analysis and nearest-neighbor analysis of the DNA are as expected for a complement of 5S RNA, indicating that the entire 5S sequence is copied. The complementary DNA hybridizes to 5S RNA with a R0t1/2 of 8.9 X 10(-4) mol.s.L-1. No hybrid is formed with Escherichia coli 16S and 23S ribosomal RNA, E. coli 5S ribosomal RNA, yeast transfer RNA, rat liver transfer RNA, or rat liver 18S and 28S RIBOSOMAL RNA. The Tm of the 5S RNA:5S DNA hybrid in 15 mM NaCl containing 1.5 mM sodium citrate is 74 degrees C, 2.5 degrees C below the theoretical melting temperature of a DNA duplex of 60% G + C. Analysis of the hybrid in buoyant density gradients also indicates that hybridization is both specific and precise. The complementary DNA anneals to calf thymus, rat liver, and salmon sperm DNAs but not to E. coli DNA. Annealing of 5S cDNA to calf thymus DNA with a C0t1/2 of 2.1 suggests that there are several thousand 5S RNA genes in the calf thymus genome (haploid). At least that number of 5S RNA genes is present in the salmon sperm genome.

Animals↗
PubMedDate not supplied

Composition and protein efficiency ratio of meat samples partially defatted with petroleum ether, acetone, or ethyl ether.

Freeze-dried beef samples were partially defatted with either petroleum ether, acetone, or ethyl ether before determination of protein efficiency ratio (PER) to study the extraction effects on the composition and protein nutritional quality of the extracted beef. Defatting a protein source, such as meat or a meat product, may often be necessary to produce a test diet that contains 10% protein and 8% fat. Amino acid, carnosine, anserine, creatine, creatinine, inosine, and proximate compositions were determined on the extracted samples. Resulting data were compared to the composition and PER data of the beef that had no solvent treatment. Although the chemical analysis data from the study showed some variation between the proteins and other nitrogenous components of the unextracted and the extracted beef, these variations were too small to affect the protein nutritional quality of the beef as measured by PER.

Acetone↗