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Salem L, Walter N, Malone R. Suppressor analysis of the Saccharomyces cerevisiae gene REC104 reveals a genetic interaction with REC102. Genetics 1999; 151:1261-72. [PMID: 10101155 PMCID: PMC1460571 DOI: 10.1093/genetics/151.4.1261] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
REC104 is a gene required for the initiation of meiotic recombination in Saccharomyces cerevisiae. To better understand the role of REC104 in meiosis, we used an in vitro mutagenesis technique to create a set of temperature-conditional mutations in REC104 and used one ts allele (rec104-8) in a screen for high-copy suppressors. An increased dosage of the early exchange gene REC102 was found to suppress the conditional recombinational reduction in rec104-8 as well as in several other conditional rec104 alleles. However, no suppression was observed for a null allele of REC104, indicating that the suppression by REC102 is not "bypass" suppression. Overexpression of the early meiotic genes REC114, RAD50, HOP1, and RED1 fails to suppress any of the rec104 conditional alleles, indicating that the suppression might be specific to REC102.
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Chandler SH, Turman J, Salem L, Goldberg LJ. The effects of nanoliter ejections of lidocaine into the pontomedullary reticular formation on cortically induced rhythmical jaw movements in the guinea pig. Brain Res 1990; 526:54-64. [PMID: 1706638 DOI: 10.1016/0006-8993(90)90249-b] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In the ketamine/urethane anesthetized guinea pig, electromyographic (EMG) responses of the anterior digastric muscle were studied when loci within the lower brainstem were microejected with lidocaine (2%) during rhythmical jaw movements (RJMs) evoked by repetitive electrical stimulation of the masticatory area of the cortex. The area investigated was between the trigeminal motor nucleus (Mot V) and the rostral pole of the inferior olive. Microejections of lidocaine, contralateral to the cortical stimulus site, into the ventral-medial portion of Mot V where digastric motoneurons are known to be located, resulted in reduction or complete abolishment of the digastric EMG activity ipsilateral to the ejection with no effective change in mean cycle duration (CD) or mean percent normalized integrated amplitude of the contralateral digastric EMG. Microejections of lidocaine, contralateral to the cortical stimulus site, into the ponto-medullary reticular formation in areas that included portions of the caudal nucleus pontis caudalis (PnC), nucleus gigantocellularis (GC), medial nucleus parvocellularis (PCRt), and dorsal paragigantocellularis (dPGC), in most cases produced a bilateral reduction in the mean normalized integrated amplitude and a bilateral increase in the mean cycle duration. In these sites, the bilateral increase in mean cycle duration of digastric EMG bursts was also associated with a significant increase of coefficient of variation in CD. In many cases, microejection of lidocaine completely abolished rhythmical digastric activity, bilaterally. HRP injections into Mot V were performed to determine the locations of trigeminal premotoneurons and their relationship to effective lidocaine sites for rhythmical jaw movement suppression. Retrogradely labeled cells were found mainly in the mesencephalic nucleus of V; trigeminal principal and spinal V sensory nuclei, bilaterally; and within the intermediate and lateral regions of reticular formation, bilaterally. No labeling was found in the medial reticular formation, including the nucleus gigantocellularis and dorsal paragigantocellularis.(ABSTRACT TRUNCATED AT 400 WORDS)
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Salem L, Berthier G, Lefour JM, Koga T, Durup J. Reply Reply to a comment on “overlap revisited”. Chem Phys Lett 1990. [DOI: 10.1016/0009-2614(90)87164-m] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Knowles JB, MacLean AW, Vetere C, Young P, Salem L, Surridge-David M, Coulter M. The influence of prior wakefulness on REM sleep. J Biol Rhythms 1987; 2:81-93. [PMID: 2979656 DOI: 10.1177/074873048700200201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Data from studies of naps and of shifted sleep were used to determine the relationship between two measures of rapid eye movement (REM) sleep (percentage of REM in the first 2 hr of sleep and REM latency) and prior wakefulness. For each sample, we calculated the difference between the observed value and that predicted by a cosine function that estimated the circadian rhythm of REM sleep propensity. The difference values were found to correlate reliably with hours and log hours of prior wakefulness. We conclude that while REM sleep is regulated in part by an endogenous circadian oscillator, it is also influenced by the duration of prior wakefulness.
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Knowles JB, MacLean AW, Salem L, Vetere C, Coulter M. Slow-wave sleep in daytime and nocturnal sleep: an estimate of the time course of "Process S". J Biol Rhythms 1986; 1:303-8. [PMID: 2979592 DOI: 10.1177/074873048600100404] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Daan et al. (1984) have proposed that sleep and wakefulness are regulated, in part, by a "Process S" that increases during wakefulness and declines during sleep. Data derived from several studies were taken to determine the time course of Process S during both wakefulness and sleep. As required by the model, slow-wave-sleep (SWS; an index of Process S) was found to increase exponentially as a function of prior wake time (equation 1) and to decline exponentially as a function of time asleep (equation 2). The equations accounted for 91% and 96% of the variance, respectively. In addition, equation 1 accurately predicted the amount the amount of SWS in the first hour of nocturnal sleep.
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Salem L. Dissolution of an “adsorbate” level into a band of “catalyst” levels. J Electroanal Chem (Lausanne) 1985. [DOI: 10.1016/0368-1874(85)80040-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Salem L, Elliott R. The finite and infinite cubes as models for understanding heterogeneous catalysis. ACTA ACUST UNITED AC 1983. [DOI: 10.1016/0166-1280(83)80092-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Salem L, Elliott R. The finite and infinite cubes as models for understanding heterogeneous catalysis. J Mol Struct 1983. [DOI: 10.1016/0022-2860(83)90388-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Abstract
Although the great number of electronic states available to an excited molecule might seem to preclude a coherent picture of photochemical reaction mechanisms, it is possible to bring out some basic features common to a great many reactions. The electronic states of the primary diradical intermediates, surface crossings, topicity, and avoided surface crossings have been shown to be essential components of the electronic theory of photochemical reactions. Diradicals have four important electronic states. Knowing these states, and making a simple electron count, it is possible to draw state correlation diagrams. Some diagrams show a typical surface crossing of the ground singlet state with the lowest (singlet, triplet) pair of excited states, with clear-cut consequences of quantum yields under various conditions. In other reactions the surfaces stay apart. The critical discriminating feature that determines the type of correlation diagram is the topicity. Photochemical reactions can be classified according to topicity, which is useful in interpreting their mechanisms (53). Avoided surface crossings can also be classified into different types. Figure 7, which illustrates the interplay of a covalent and an ionic surface responsible for photochemical electron transfer, is a typical multidimensional representation of a photochemical reaction. The chemical behavior of the excited zwitterionic states of common intermediates, such as twisted ethylene or diallyl, reflects the quantum mechanical nature of photochemical processes. In these states, for perfectly symmetric systems, charge oscillates back and forth between two symmetry-equivalent sites. Slight geometric perturbations can create a sudden polarization of the excited molecule, with localization of almost a full charge at one end of the molecule. A photon is transformed into an electrical signal thanks to an appropriate molecular distortion. Nature may have used this simple process in the N-retinylidene visual chromophore to trigger an electrical response to vision.
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Salem L, Bruckmann P. Conversion of a photon to an electrical signal by sudden polarisation in the N-retinylidene visual chromophore. Nature 1975; 258:526-8. [PMID: 1196385 DOI: 10.1038/258526a0] [Citation(s) in RCA: 107] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Ballhausen J, Cotton FA, Eschenmoser A, Havinga E, Hoffman R, Huisgen R, Khorana HG, Lehn JM, Linnett JW, Salem L, Wilkinson G. Too Many Chemistry Journals. COLLEGE & RESEARCH LIBRARIES 1974. [DOI: 10.5860/crl_35_04_268] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Eisenstein O, Anh NT, Jean Y, Devaquet A, Cantacuzène J, Salem L. Lone pairs in organic molecules: Energetic and orientational non-equivalence. Tetrahedron 1974. [DOI: 10.1016/s0040-4020(01)97305-3] [Citation(s) in RCA: 103] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Salem L, Hoffmann R, Otto P. The Energy of Substituted Ethanes. Asymmetry Orbitals. Proc Natl Acad Sci U S A 1973; 70:531-2. [PMID: 16592060 PMCID: PMC433298 DOI: 10.1073/pnas.70.2.531] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The leading terms in the energy of a general substituted ethane are derived in explicit form as a function of the torsional angle
θ
, the substituent electronegativities, and their mutual overlaps. The energy is found to be the sum of all four overlaps between pairs of asymmetry orbitals, and satisfies the requisite symmetry properties.
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Devaquet A, Salem L. Potential Energy- Sheets for the nπ* and ππ* Triplet States of Acrolein. CAN J CHEM 1971. [DOI: 10.1139/v71-160] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The energy of the nπ* and ππ* triplet states of acrolein as a function of the twist of the CH2 terminal groups and relaxation of the three skeletal σ bonds has been investigated in an "ab initio" self-consistent field formalism. The potential energy sheets of these triplets show that the cis photoadducts of cyclic enones may arise from "planar, relaxed" triplet states whereas the trans photoadducts are given by "twisted, unrelaxed" triplet states.
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Zucker IJ, Klein ML, Barker JA, Rice OK, Barron THK, Guggenheim EA, Reissland JA, Salem L, Brzostowski W, Baughan EC, Longuet-Higgins HC, Jansen L, Luck WAP, Murrell JN, Munn RJ, Rowlinson JS, Saville G, Weir RD, Smith EB, Rigby M. General discussion. ACTA ACUST UNITED AC 1965. [DOI: 10.1039/df9654000117] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Salem L, Wilson EB. Reliability of the Hellmann—Feynman Theorem for Approximate Charge Densities. J Chem Phys 1962. [DOI: 10.1063/1.1732475] [Citation(s) in RCA: 50] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Abstract
The various long-range forces which are effective between molecules in their electronic ground states are examined. Orders of magnitude are given for those forces which should occur in the interaction of lipide and protein chains. It is found that electrostatic forces should be responsible for bringing and holding together protein and lipide components, but London – Van der Waals dispersion forces are probably of paramount importance in maintaining the lipide chains together in micelles or double layers.Special attention is drawn to the dispersion forces and to the conditions under which these forces are locally additive; one can calculate accurate values of the dispersion energy of interaction between saturated hydrocarbon chains at short distances (a few angstroms apart) by adding all the bond–bond interactions. A general expression is given for the dispersion energy between two parallel and opposed chains built out of identical units, and numerical values are given for the case of closely packed hydrocarbon chains.The total attraction energy is extremely sensitive to the intermolecular distance. The role of this "distance-specificity" in interactions involving unsaturated fatty acid chains and its contribution to the stability of lipoproteins is briefly examined.
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