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Biomedical subjects

A G Anderson

Publications and source records attributed to A G Anderson.

8 recordsLinked to original sources
PubMed1992

Differential helix propensity of small apolar side chains studied by molecular dynamics simulations.

A series of oligoalanine molecules with single amino acid replacements in the middle of the chain has been studied by molecular dynamics simulations. Differences in stability of the alpha-helix (as free energies delta delta G degrees) were estimated for the following series of residues: alpha-aminoisobutyric acid, alanine, alpha-amino-n-butyric acid, valine, glycine, D-alanine, t-leucine (= alpha-amino-beta,beta-dimethyl-n- butyric acid), and proline, arranged here in decreasing order of helix-forming potential. (The results for proline and valine had been reported earlier.) No experimental results were available for alpha-amino-n-butyric acid, D-alanine, and t-leucine at the time these calculations were done. The values of delta delta G degrees, including the three predictions, are in striking agreement with recent experimental results. A combination of free dynamics, dynamics with forced conformational change, and dynamics with forced molecular replacement was used. Conformational distributions were calculated for the peptide backbone of the dipeptides and, where appropriate, for the side chains of the dipeptide and the alpha-helix. The results demonstrate an unexpected level of accuracy for the all-atom model used to represent atomic interactions in the simulations. The simulations permit a detailed analysis of different factors responsible for conformational preferences and differences in stability. These conclusions drawn from this analysis agree with accepted qualitative explanations and allow these explanations to be quantitated to an extent not heretofore possible.

Alanine↗
PubMed1988

Fractures of the medial infraorbital rim.

Fractures of the medial infraorbital rim may occur independently or in conjunction with fractures of the nose and zygoma. Infraorbital fractures are frequently associated with anesthesia in the distribution area of infraorbital nerve and can produce palpable "step-off" deformities. Because roentgenographic and clinical indications of these fractures are often subtle, such injuries may go unrecognized in the presence of more obvious nasal fractures or may be misdiagnosed as "tripod" fractures. A proper recognition of these fractures is necessary for correct diagnosis and treatment. Three cases are presented and seven cases are summarized.

Adolescent↗
PubMed1988

Microfolding: conformational probability map for the alanine dipeptide in water from molecular dynamics simulations.

A direct attack on the protein-folding problem has been initiated with the free energy perturbation methods of molecular dynamics. The complete conformational probability map for the alanine dipeptide is presented. This work uses the SPC model for the explicit hydration of the dipeptide. Free energy differences for the four observed minima (beta, alpha R, alpha L, C7ax) are given, and the free energy barriers between minima are outlined.

Dipeptides↗
PubMed1983

Techniques to enhance utilization of advancement flaps.

Utilization of advancement flaps to cover facial defects is potentially limited by the secondary distortion of adjacent anatomical landmarks, expansion of any residual lesion, and the vascular embarrassment of wound closure under tension. In this study, advancement flaps are raised in piglets, and the first stage in the serial excision of a hypothetical skin lesion is simulated. It is demonstrated that undermining of the lesion-bearing skin results in expansion of the lesion and is counterproductive. If, however, a separate layer of hypodermis and fascia is mobilized deep to the lesion and sutured to the advancing flap, skin closure can be accomplished with minimal tension. This results in maximal recruitment of the advancement flap and minimal expansion of the residual lesion as the defect is bridged.

Animals↗
PubMed1977

Effects of ionic and nonionic detergents on antigen-antibody reactions.

Using highly sensitive and quantitative radioimmunoassay procedures we have measured the effects of different concentrations of three commonly used detergents, SDS, DOC, and Triton X-100, on antibody-antigen reactions. Triton X-100, had a relatively mild effect on primary antigen-antibody bindings, the precipitin reaction, and a double antibody RIA as evidenced by only an 8 to 10% inhibition of binding or precipitation. These results were not detergent concentration dependent, as Triton concentrations ranging from 5 to 0.1% had virtually no differential effects. Sodium deoxycholate (DOC) had a more profound effect on both primary antigen-antibody binding and the precipitin reaction than did Triton X-100, and its effects, unlike those of Triton X-100, were concentration dependent. There was a direct relationship between concentration of DOC and degree of inhibition of both primary binding and immune precepitation especially in antigen excess. Sodium dodecylsulfate (SDS), at concentrations 10- to 100-fold less than either Triton X-100 or DOC, had profound inhibitory effects on primary antigen-antibody binding, the precipitin reaction, and a double antibody radioimmunoassay. Generally, at concentrations greater that 0.01% SDS, almost all immunochemical reactivity is destroyed.

Animals↗