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Grid search conformational analysis of carnitine and acetylcarnitine

Carnitine has physiologically important function of decreasing triglycerides content, very low density lipoproteins and cholesterol. Considering these facts, it may be important in the reduction of cardiovascular dieseases. Initial geometries for the conformational analysis of carnitine were obtained by systematic search of potential energy surfaces (PES) scans calculated at the semiempirical level. PES were spanned in the space of five and six torsional coordinates for carntine. Optimization procedure for finding strict local minima utilizing a brute-force search for arbitrary number of ways (n-way space) was applied and all strict local minima on PES were identified. These local minima found at the semiepmirical level were subsequently optimized using density functional theory (B3LPY-D3/6- 311++G(d.p)). To ensure that optimized structures were indeed local minima, harmonic frequency calculations were carried out and normal modes were examined visually. Full conformational spacews were determined and all conformers were structurally examined and their relative content at the room temperature were determined from Maxwell-Boltzmann distribution. Furthermore, the potential for internal rotation of trimethylamino group in both molecules will be calculated and analyzed.

grid search, conformational analysis, potential energy surfaces, carnitine

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