William Egan

Proton and deuterium NMR of hydrogen bonds: Relationship between isotope effects and the hydrogen bond potential

Abstract The difference in chemical shift between hydrogen bonded protons and deuterons has been examined both theoretically and experimentally. It is shown that valuable information about the hydrogen bond potential can be extracted from this isotope effect on chemical shifts.

New NHR Techniques for Structure Determination and Resonance Assignments of Complex Carbohydrates

Abstract This paper describes several new NMR techniques for structure determination and spectral assignment of polysaccharides. Positions of linkages between sugar units can be determined unambigously and with high sensitivity using a modified version of the well known INEPT experiment. A new two-dimensional experiment is shown to provide excellent resolution and sensitivity in correlating 1H and 13C chemical shifts.

Synthesis of acyloxyalkyl acylphosphonates as potential prodrugs of the antiviral, trisodium phosphonoformate (foscarnet sodium)

Abstract Bis(trimethylsilyl) acylphosphonates via their silver salts couple with iodoalkyl esters to provide an efficient synthesis of the corresponding acyloxyalkyl esters as potential prodrugs of the antiviral agent, trisodium phosphonoformate. These compounds were tested as inhibitors of HIV-1 in chronically infected H9 cells.

New N.M.R.-spectroscopic approaches for structural studies of polysaccharides: Application to the Haemophilus influenzae type a capsular polysaccharide

The extension of several modern nuclear magnetic resonance (n.m.r.) spectroscopic techniques to polysaccharides is discussed and illustrated, using the native Haemophilus influenzae type a capsular polysaccharide. These techniques provide for the unambiguous assignment of all n.m.r. resonances (1H, 13C, and 31P) via high-sensitivity homonuclear and 1H-detected heteronuclear correlations, and they are capable of locating the intersaccharide linkages (both O-linked and phosphoric diester-linked) and appended groups (e.g. O-acetyl groups). To illustrate the power and sensitivity of these methods, a 10-mg sample of the H. Influenzae type a polysaccharide (repeat unit mol. wt. = 376) was studied. The combined acquisition time for the two-dimensional 1H-13C correlation data (one-bond and multiple-bond), the 1H-31P correlation data, and the 1H-1H (homonuclear Hartmann-Hahn) data was approximately 18 h.

Structural studies of the Haemophilus influenzae type e capsular polysaccharide.

The structure of the Haemophilus influenzae type e capsular polysaccharide has been determined by a combination of chemical and spectroscopic methods. The structure of the repeating unit of the polymer was found to be leads to 3)-beta-D-GlcNAc-(1 leads to 4)-beta-D-ManANAc-(1 leads to ; both sugars were present in the pyranoid form.

Structural and immunological studies of the Escherichia coli K7 (K56) capsular polysaccharide

The structure of the Escherichia coli K7 capsular polysaccharide has been investigated by a combination of chemical and spectroscopic methods. The Structure of the repeating unit of the polymer was found to be goes to 3)-beta-D-ManNAcA-(1 leads to 4)-beta-D-Glc-(1 goes to ; the O-6 atom of the D-glucosyl residue in the repeating unit is acetylated. The K7 polysaccharide is cross-reactive with the Streptococcus pneumoniae type 3 polysaccharide, the structure of which had previously been determined; our n.m.r. studies of the S. pneumoniae type 3 polysaccharide are in accord with this structure. The E. coli K7 and K56 capsular antigens have been shown by serology and 13C-n.m.r. spectroscopy to be identical.

Determination of the structure of the Escherichia coli K100 capsular polysaccharide, cross-reactive with the capsule from type b Haemophilus influenzae

The structure of the Escherichia coli K100 capsular polysaccharide, cross-reactive with that from type b Haemophilus influenzae, was determined by using a combination of chemical and spectroscopic techniques. The structure of the K100 repeating unit was found to be----3)-beta-D-Ribf-(1----2)-D-ribitol-5-(PO4----. The K100 polysaccharide is thus identical in composition to, but different in linkage from, the H. influenzae type b capsular polysaccharide, which has beta-D-Ribf-(1----1)-D-ribitol linkages.

Structural studies of the Escherichia coli K93 and K53 capsular polysaccharides

The structures of the Escherichia coli K93 and K53 capsular polysaccharides have been investigated by chemical and spectroscopic methods. The repeating unit of both polymers was found to be----3)-beta-D-Galf-(1----f)-beta-D-GlcAp-(1. The O-5 and O-6 atoms of D-galactose are acetylated in the repeating unit of the K93 polymer, but only O-2 is acetylated in the K53 polymer. The K93 polysaccharide is cross-reactive with the Neisseria meningitidis Group A capsular polysaccharide (of known structure). The K53 polysaccharide, although structurally similar to that from K93 organisms, does not cross-react with the Group A polymer.

31P-NMR studies of Mycoplasma gallisepticum cells using a continuous perfusion technique

31P‐NMR studies of Mycoplasma gallisepticum cells have been carried out using a continuous perfusion technique; these are the first such studies with this organism. Using this technique, glucose metabolism was monitored in the intact organisms, and cell extracts were prepared to identify the intermediates. Under glycolytic conditions, high levels of fructose‐1,6‐diphosphate were observed, indicating that this sugar may play a key role in the regulation of metabolism. The level of phosphoenolpyruvate was low under normal glycolytic conditions, and did not increase during starvation. From the position of the internal inorganic phosphate peak, the intracellular pH was estimated. The cells were found to maintain an intracellular pH of ~ 7.1 over an investigated external pH range of 6.6–8.6.

Extended diffusion of rigid asymmetric molecules

The extended diffusion theory of molecular motions in fluids has been applied to the case of rigid asymmetric molecules. Illustrative calculations of the second rank reorientational correlation time matrix and the correlation factors associated with NMR spin‐rotation relaxation are presented as functions of the angular momentum correlation time. Analytic expressions for these correlation times and factors in the diffusion limit are also given.