PubMed Health⌕ Search

Biomedical subjects

H Noller

Publications and source records attributed to H Noller.

7 recordsLinked to original sources
PubMed1994

RNA modeling using Gibbs sampling and stochastic context free grammars.

A new method of discovering the common secondary structure of a family of homologous RNA sequences using Gibbs sampling and stochastic context-free grammars is proposed. Given an unaligned set of sequences, a Gibbs sampling step simultaneously estimates the secondary structure of each sequence and a set of statistical parameters describing the common secondary structure of the set as a whole. These parameters describe a statistical model of the family. After the Gibbs sampling has produced a crude statistical model for the family, this model is translated into a stochastic context-free grammar, which is then refined by an Expectation Maximization (EM) procedure to produce a more complete model. A prototype implementation of the method is tested on tRNA, pieces of 16S rRNA and on U5 snRNA with good results.

Animals↗
PubMed1985

Further characterization of the extremely small mitochondrial ribosomal RNAs from trypanosomes: a detailed comparison of the 9S and 12S RNAs from Crithidia fasciculata and Trypanosoma brucei with rRNAs from other organisms.

We have determined the nucleotide sequence of a maxi-circle segment from the insect trypanosome Crithidia fasciculata mitochondrial DNA, on which the genes for the major maxicircle transcripts of 9S and 12S are localized. The 5'-terminal sequences of these RNAs were determined by wandering spot analysis. The map coordinates of the 9S and 12S RNAs from Trypanosoma brucei were adjusted with respect to a previous report with the aid of primer extension analysis with reverse transcriptase. This approach allowed us to align the corresponding genes from both organisms which show an overall sequence homology of 77%. The 9S and 12S RNA genes from the two trypanosome species contain sequences, closely related to some of the regions that are universally conserved among ribosomal RNAs from members of the three primary kingdoms and their organelles, even though the overall level of sequence homology is extremely low. These universal sequences occur at positions in the 9S and 12S RNAs that are analogous to those occupied by their counterparts in authentic ribosomal RNAs. The characteristic secondary structure elements flanking these universal sequences in genuine ribosomal RNAs can also be formed in the trypanosomal 9S and 12S RNAs. These results provide unequivocal evidence for a ribosomal function of the 9S and 12S RNAs of trypanosomal mitochondria, notwithstanding their extremely small size (estimated to be 612 and 1141 nucleotides in C. fasciculata, 611 and 1150 nucleotides in T. brucei) and their unusual base composition (83% A+U).

Animals↗
PubMed1983

General properties of 14C-L-Valine-binding to human brain tissue.

L-Valine (VAL) binding is saturable, reversible, linear within a protein concentration of 0.2 to 0.8 mg prot./ml, pH dependent (pH-optimum 7.1 to 7.4), temperature dependent with extremely low binding at 0-4 degrees C; the assay runs at 37 degrees C; it is ion dependent (Bmax:CaCl2 (5mM): + 100%; NaCl (5 mM): -50%); very sensitive to TRITON X-100 (Bmax at 0.01%; -70%); N-ethylmaleimide (0.5 mM): Competitive inhibition; no change in non-specific binding; there are no effects by puromycin plus GTP; VAL binds to synaptic membranes of human frontal cortex with KD-values several fold lower than that observed with homogenates, the distribution of VAL-binding is different in various human brain areas and can be inhibited by L-leucine, L-isoleucine, L-serine, DL-threonine, glycine and D-valine, while aromatic amino acids, beta-alanine, GABA, taurine, glutamate, proline and gamma-glutamyltaurine have no effects of 10(-3) M.

Aged↗