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We have developed a new representation for structural and functional motifs in protein sequences based on correlations between pairs of amino acids and applied it to alpha-helical and beta-sheet sequences. Existing probabilistic methods for representing and analyzing protein sequences have traditionally assumed conditional independence of evidence. In other(More)
We have previously shown that varying the N-terminal amino acid in alpha-helical peptides can cause large variations in helix content (Chakrabartty et al., 1993a). The Lifson-Roig theory for the helix-coil transition predicts, however, that substitutions at the N-terminus in an unacetylated peptide should have no effect on alpha-helix stability. We have(More)
The Wisconsin Card Sorting Test (WCST) is a neuropsychological test, hypothesized to be an indicator of dorsolateral prefrontal cortex (DLPFC) functioning. The performance of schizophrenic patients in our sample (off medication) was worse than the performance of healthy controls in all variables of the WCST, including perseverative responses (PR) as well as(More)
We wish to identify genes associated with disease. To do so, we look for novel genes whose expression patterns mimic those of known disease-associated genes, using a method we call Guilt-by-Association (GBA), on the basis of a combinatoric measure of association. Using GBA, we have examined the expression of 40,000 human genes in 522 cDNA libraries, and(More)
Whether hydrogen bonds between side chains are energetically significant in proteins and peptides has been controversial. A method is given here for measuring these interactions in peptide helices by comparing the helix contents of peptides with 1, 2, or 3 interactions. Results are given for the glutamine--aspartate (i, i + 4) hydrogen-bond interaction. The(More)
Late-onset depression (greater than or equal to 60 years) is believed to be less associated with a risk of depression in first-degree relatives than early-onset depression. However, family studies in elderly probands fitting the current methodological standards of family studies are not available. The reported family study in geriatric inpatients with(More)
In a search for an external validation of the negative syndrome construct and the attentional impairment item on Andreasen's scale, 49 unmedicated schizophrenic patients were administered the Span of Apprehension Test and a Continuous Performance Test with two levels of difficulty. This schizophrenic sample performed significantly more poorly on the(More)
The therapeutic effect of the alpha 2-antagonist yohimbine in erectile dysfunction was studied in a double-blind placebo-controlled design. Thirty-one male patients underwent extensive clinical, urological, and psychiatric diagnosis and were dichotomically classified into an organic and a nonorganic subgroup. Following a 1-week placebo run-in period,(More)
Using a new representation for interactions in protein sequences based on correlations between pairs of amino acids, we have examined alpha-helical segments from known protein structures for important interactions. Traditional techniques for representing protein sequences usually make an explicit assumption of conditional independence of residues in the(More)