Mark Needels

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We have prepared a library of approximately 10(6) different peptide sequences on small, spherical (10-microns diameter) beads by the combinatorial chemical coupling of both L- and D-amino acid building blocks. To each bead is covalently attached many copies of a single peptide sequence and, additionally, copies of a unique single-stranded oligonucleotide(More)
Phosphomannose Isomerase (PMI) has been shown by genetic methods to be an essential enzyme in fungal cell wall biosynthesis. The PMI inhibitor AF14049 was discovered as an unanticipated side product from high-throughput library screening against the enzyme from C, albicans. Solid-phase synthetic methods were developed and a series of libraries and discrete(More)
Aminoacylation of the "internal" 2'hydroxyl groups of poly(A) with the imidazolide of racemic DL-leucine resulted in the formation of an enantiomeric excess of the D-ester, whereas aminoacylation with the imidazolide of racemic N-3,5-dinitrobenzoyl-DL-leucine gave an enantiomeric excess of the L-ester. Comparison of these results with those obtained(More)
Plausible mechanisms exist for the amplification of an enantiomeric excess in prebiotic oligonucleotides and peptides, but whether there is a causal relationship between the chirality of present-day nucleic acids and proteins is not known. We have found that aminoacylation of the "internal" hydroxyl group of a dinucleoside monophosphate can occur(More)
The use of volumetric rendering for interpreting the computed electronic structure of solids is discussed. The structure, manifested as an atomic-scale 3-D electronic charge density, is computed from a pure mathematical model. The mathematical technique represents a class of ab initio computations that predict the atomic structure by solving the equations(More)
The arginine at position 200 of EcoRI endonuclease is thought to make two hydrogen bonds to the guanine of the sequence GAATTC and thus be an important determinant of sequence discrimination. Arg-200 was replaced by each of the other 19 naturally occurring amino acids, and the mutant endonucleases were assessed for activities in vivo and in vitro. The(More)
There has been much speculation about the types of molecules that were present in the first living forms. Recent discoveries show that RNA is a more versatile molecule than was previously believed, but whether it was ever able, for example, to synthesize its own monomers from available precursors is not yet known. If amino acids coexisted with nucleosides(More)
Understanding the properties of surfaces of solids and the interactions of atoms and molecules with surfaces is extremely important from both a technological and academic point of view. The recent advent of ultrahigh vacuum technology has made microscopic studies of well-characterized surface systems possible. The way atoms move to reduce surface energy,(More)
We apply volumetric rendering to the interpretation of atomic-scale data generated from quantum molecular dynamics computations. In particular, we examine silicon computations, and we discover that volumetric visualization of the computed 3D electronic charge density is a valuable tool for identifying defect states in silicon lattices in which oxygen atoms(More)
Neither of these is "solved", although parts of some published models now suggest reasonable answers. Understanding the first part may be a necessary step to solving the second, although this is not universally believed. Significant correlations have been found between some properties of amino acids and the related properties of their anticodonic(More)
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