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L Gorelic

Publications and source records attributed to L Gorelic.

14 recordsLinked to original sources
PubMed1993

A statistical model validating triage for the peer review process: keeping the competitive applications in the review pipeline.

Triage of grant application at the National Institutes of Health (NIH) is a process whereby an initial screening of applications by a scientific peer review group eliminates applications that are not competitive for awards. The process of application triage has been limited to those applications submitted to the NIH in response to an RFA (Request for Applications). A hypergeometric model was developed to determine the extent to which five, six, seven, or eight member triage teams or subsets of 12-to-20 member full committees could provide a statistically defensible triage decision. Although the intent of triage is to remove from review those applications that are noncompetitive, the model was weighted in favor of the applicant to minimize the likelihood that highly competitive applications would be eliminated. Within the assumptions and rules developed, it was determined that there was little likelihood that the latter would occur. For example, in the worst case scenario, the greatest probability that a highly competitive application would be knocked out of competition is P < or = 0.014 in the case of a five-member triage subset of a 20-member committee. Using the latter case, the model was tested on a set of 73 applications that were submitted to the National Cancer Institute for action at the February 1993 National Cancer Advisory Board. The model selected for triage required that each application be assigned to five reviewers, that each reviewer be blinded to the review assignments of the other reviewers, and that four noncompetitive votes be registered to triage out an application. Each of 19 applications received four to five noncompetitive votes, and were triaged out of the review process. The remaining 54 applications were then reviewed according to the usual NIH review process. Four of the applications received three noncompetitive triage votes each and were either rated as not recommended for further consideration (NRF, n = 2)) or received priority scores > or = 250 (n = 2) (The smaller the priority score the better the technical merit). Thirteen of the 53 applications received two noncompetitive votes. Of the latter, two were not recommended for further consideration and the remaining 11 received priority scores between in excess of 200. The distribution of competitive applications was such that funding was limited to those applications with priority scores of less than 190. Thus, the data suggest that the conservative model is valid such that the likelihood of eliminating a highly competitive application from consideration for funding is remotely small.(ABSTRACT TRUNCATED AT 400 WORDS)

Competitive Bidding↗
PubMed1982

Uridine 5'-phosphate photohydrate formation in irradiated Escherichia coli 30S ribosomes: photochemistry and relation to ribonucleic acid-protein cross-linking.

Irradiation of aqueous buffered solutions of Escherichia coli 30S ribosomes with doses of 254-nm radiation greater than 10(19) quanta causes formation of uridine 5'-phosphate (UMP) photohydrates in ribosomal 16S RNA (rRNA). The number of molecules of UMP photohydrate formed at doses less than 2 x 10(20) quanta is linearly dependent on dose of absorbed 254-nm radiation. Maximum UMP photohydrate formation is dependent on initial ribosome concentration. When solutions containing 1 A260 unit of 30S ribosomes/mL were irradiated with greater than 2 x 10(20) quanta of 254-nm radiation, maximum photohydrate formation was equal to 47 residues/ribosome. Irradiation of solutions containing 2 A260 units/mL with greater than 7 x 10(20) quanta caused formation of 102 UMP photohydrates/ribosome. These values correspond to conversion of either 15 or 33%, respectively, of the total UMP content of 30S ribosome 16S rRNA to photohydrates. Target theory analysis of UMP photohydration in 30S ribosomes showed that UMP photohydrates are formed by single-hit kinetics from two photochemically distinct precursors. Of the total 16S rRNA UMP residues, 10% was included in the most rapidly (low dose) reacting fraction. The respective photohydration cross sections are 0.014 (low dose) and 0.0095 cm2/muEinstein (high dose) for ribosome solutions containing 2 A260 units/mL. UMP photohydrate content of irradiated 30S ribosomes was compared with that of previous data for the extent of RNA-protein cross-linking at equivalent doses of absorbed 254-nm radiation. This comparison showed that at least two UMP photohydrates form per RNA-protein cross-linking event in 30S ribosomes irradiated with a dose of 254-nm radiation (1.5 x 10(19) quanta), which causes cross-linking of only three ribosomal proteins to 16S rRNA.

Bacterial Proteins↗
PubMed1978

Studies of the effects of ultraviolet radiation on the structural integrities of ribosomal RNA components of the Escherichia coli 50S ribosomal subunit.

The effects of 254-nm radiation on the structural integrities of free and 50S ribosome-bound 5S and 23S ribosomal ribonucleic acids (rRNA) have been elucidated. Irradiation of aqueous solutions of Escherichia coli 50S ribosomes with 253.7-nm radiation results in the formation of single-strand breaks in double-stranded regions of the 23S rRNA component, but not in rRNA chain scission, and destabilization of the secondary structure of the 23S rRNA toward denaturation. The minimum doses of 253.7-nm radiation required for the first detection of the two effects are 7 x 10(19) quanta for the production of single-strand breaks in double-stranded regions of the 23S rRNA, and less than 2.3 x 10(19) quanta for destabilization of the 23S rRNA secondary structure. Free 23S rRNA is resistant toward photoinduced chain breakage at doses of 253.7-nm radiation up to at least 2.3 x 10(20) and is much less sensitive toward destabilization of secondary structure than ribosome-bound 23S rRNA toward chain breakage, 50S ribosome-bound 5S rRNA is resistant toward chain breakage at doses of 253.7-nm radiation up to at least 2.3 x 10(20) quanta. Ribosome-bound 5S and 23S rRNA are also not photosensitive toward intermolecular 5S/23S rRNA crosslinkage.

Escherichia coli↗
PubMed1976

Demonstration of ribosome-dependent photoinduced chain breakage of the 16S ribosomal ribonucleic acid component of the Escherichia coli 30S ribosomal subunit.

The effects of 253.7-nm radiation on the structural integrities of free and ribosome-bound 16S ribosomal ribonucleic acid (rRNA) have been elucidated. Exposure of aqueous solutions of Escherichia coli 30S ribosomal subunits to 253.7-nm radiation results in RNA-chain scission and the formation of single-stranded breaks in double-stranded regions of the ribosome-bound 16S rRNA. The minimum doses of incident 253.7-nm radiation required for the first detection of the two types of RNA chain breaks are 2 X 10(20) quanta for single-strand breaks in double-stranded regions of the ribosome-bound 16S rRNA,and at least 5 X 10(20) quanta for RNA-chain scission. In contrast to the photosensitivity of ribosome-bound 16S rRNA toward chain breakage, free 16S rRNA seems to be resistant toward photoinduced chain breakage at doses of incident 253.7-nm radiation up to at least 10(21) quanta.

Escherichia coli↗
PubMed1976

Analysis of the kinetics of photoinduced crosslinkage of the protein and RNA components of the Escherichia coli 50 S ribosomal subunit.

The kinetics of photoinduced crosslinkage of the protein and ribosomal RNA components of the Escherichia coli 50 S ribosomal subunit were determined by two-dimensional gel electrophoresis. One group of ribosomal proteins was found to be reactive in the crosslinkage reaction at doses of 254 nm radiation of 2.9 X 10(3) ergs-mm-2. A second group of 50-S ribosomal proteins was found to be unreactive in the crosslinkage reaction at doses of 254 nm radiation less than 8.6 X 10(6) ergs-mm-2, but were reactive at higher doses.

Dose-Response Relationship, Radiation↗
PubMed1976

Photoinduced cross-linkage, in situ, of Escherichia coli 30S ribosomal proteins to 16S rRNA: identification of cross-linked proteins and relationships between reactivity and ribosome structure.

The kinetics of photoinduced cross-linkage of Escherichia coli 30S ribosomal proteins to the 16S-rRNA molecule in the intact Escherichia coli 30S ribosomal subunit was studied in this report. All of the 30S ribosomal proteins become cross-linked to the 16S rRNA before changes in the sedimentation characteristics of the 30S ribosomal subunit can be detected. The proteins exhibit different reactivities in the cross-linkage reaction. One group of proteins-S3, S7-S9, S11, S12, and S15-S19-is cross-linked to the 16S rRNA by single-hit kinetics, or by photoprocesses of nonunity but low multiplicities. A second group of proteins--S1, S2, S4-S6, S10, S13, S14, and S21--is cross-linked to the 16S rRNA by photoprocesses of a complex nature. A comparison of these data with other properties of the individual 30S ribosomal proteins related to ribosome structure indicated that most of the 30S ribosomal proteins cross-linked to the 16S rRNA by photoprocesses of low multiplicities had been classified rRNA-binding proteins by nonphotochemical methods, and most of the proteins cross-linked to the 16S rRNA by photoprocesses of large multiplicities had been classified as nonbinding proteins. There were certain exceptions to these correlations. Proteins S4 and S20, both RNA-binding proteins, become cross-linked to the 16S rRNA by photoprocessses of large multiplicities, and proteins S3, S11, S12, and S18, none of which have been classified RNA-binding proteins, exhibited low multiplicities in the cross-linkage reaction. All of these exceptions could be explained in terms of limitations inherent in the photochemical methods used in this study and in other types of methods that have been used to study RNA-protein interactions in the 30S ribosomal subunit. The data presented here also suggest that labile RNA-protein cross-links are present in the uv-irradiated 30S ribosomal subunits, and that neither peptide-bond cleavage nor photoinduced modification of the charged side-chain groups in the ribosomal proteins accompanied the cross-linkage reaction. However, some photoinduced RNA-chain breakage might have occurred.

Binding Sites↗
PubMed1975

Evidence for photoinduced cross-linkage, in situ, of 30S ribosomal proteins to 16S rRNA.

The effects of ultraviolet radiation on the 30S ribosomal subunit of Escherichia coli were studied. Irradiation in aqueous solution under anaerobic conditions resulted in a dose-dependent decrease in the separability of the rRNA and protein components of the 30S ribosomal subunit in 4 M urea-3 M LiC1. The results of gel filtration studies of the irradiated ribosomes before and after treatment with pancreatic ribonuclease indicated that the decrease in separability of the ribosome components was a result of the photoinduced formation of covalent RNA-protein cross-links. The number of covalent cross-links was estimated to correspond to less than 3 per 10,000 daltons of ribosomal proteins. One-dimensional gel electrophoresis studies of the course of the photoinduced cross-linkage reaction indicated that cross-linkage of individual 30S ribosomal proteins to the 16S rRNA proceeds in two dose-dependent steps. The first step requires an input of 1 X 10(20) quanta of 253.7 -nm radiation and results in the cross-linkage of at least five ribosomal proteins to the 16S rRNA. The second step requires a total input of 2 X 10(20) quanta of 253.7 -nm radiation, and results in the cross-linkage of most of the remaining 30S ribosomal proteins to the 16S rRNA.

Bacterial Proteins↗
PubMed1975

Photoinduced convalent crosslinkage, in situ, of Escherichia coli 50 S ribosomal proteins to rRNA.

Irradiation of aqueous solutions of Escherichia coli 50 S ribosomal subunits with 253.7 nm light results in the covalent crosslinkage of the rRNA and protein components. Neither peptide bond cleavage nor protein-protein crosslinkage accompanies the crosslinkage reactionmin addition, substantial photoinduced modifications in the primary structure of the ribosomal proteins, other than crosslinkage to rRNA, are not detected. The crosslinkage of the ribosomal proteins to the rRNA proroceeds in two discrete, dose-dependent steps. The first step, requires an input of up to 3 with 10-20 Quanta of 253.7nm radiation, and results in the crosslinkage of less than half of the ribosomal proteins to the rRNA. The second step requires an input of greater than 3 with 10-20 Quanta of 253.7 nm radiation, and results in the crosslinkage of the remaining ribosomal proteins to the rRNA. The possible relationship of the nature of the corsslinkage reaction to the spatial orientations of the rRNA and protein molecules in the intact 50 S ribosomal subunits is discussed.

Bacterial Proteins↗
PubMed1971

An Escherichia coli mutant with increased messenger ribonuclease activity.

A temperature-sensitive mutant strain of Escherichia coli exhibits a remarkable increase in RNase activity when grown at its nonpermissive temperature. During growth at the nonpermissive temperature, there is an increase in the extent of breakdown of pulse-labeled RNA and a decrease in the functional lifetime of the mRNA for the lac operon. T7 RNA, which is usually stable in E. coli, is also stable in this strain at the nonpermissive temperature. It is possible that the RNase measured is part of the normal mechanism of mRNA degradation in the cell. A mechanism for mRNA degradation that requires the combined action of endonuclease(s) and 3' to 5' exonuclease(s) is proposed.

Biodegradation, Environmental↗