Possible reaction pathways of the lincomycin molecule according to the DFT calculation method

Abstract

Human-used antibiotics are eliminated from the body with little or no transformation at all. Traces of eliminated antibiotics enter the receiving environment directly since they cannot be treated in prevalent wastewater treatment facilities. Thus, wastewaters containing traces of antibiotics have to be treated accordingly. Lincomycin is subsequently isolated from Streptomyces lincolnensis. Lincomycin and its derivatives are antibiotics exhibiting biological activity against Gram-positive bacteria, and are natural antibiotics in the environment as pollutants. This study aims to predict the degradation mechanism of lincomycin molecule in the gaseous phase and aqueous media. Probable reaction path of lincomycin molecule with OH radicals was analyzed. Optimized geometry was calculated via Gauss View 5. Subsequently, the lowest energy status was determined through geometric optimization via Gaussian 09 program. Aiming to determine the intermediates in photocatalytic degradation mechanism of lincomycin, geometric optimization of the molecule was realized through DFT method. Activation energy for the probable reaction path was calculated, and their most stable state from the thermodynamic perspective determined for the gaseous phase and aqueous media. Impact of water solvent was investigated using the conductor-like screening solvation model (COSMO). The predicted mechanism was confirmed by comparison with experimental results on simple structures reported in literature.

New Insight into a Fenton-like Reaction Mechanism over Sulfidated β-FeOOH: Key Role of Sulfidation in Efficient Iron(III) Reduction and Sulfate Radical Generation

“…The MTZ degradation intermediates during the process were analyzed by gas chromatography-mass spectrometry (GC-MS/MS, TSQ 8000 Evo, Thermo). Moreover, to identify the reactive sites of MTZ attacked by • OH and SO 4 •– radicals and propose the transformation pathway of MTZ, theoretical density functional theory (DFT) calculations were adopted to predict intermediates and degradation pathways of MTZ through Gaussian 09 software equipped at the B3LYP/6-311G­(d) level . For the DFT reactivity descriptor calculations, the Fukui function is an important concept in conceptual density functional theory, which has been widely used in the prediction of the reactive site of electrophilic, nucleophilic, and radical attacks.…”

“…•− radicals and propose the transformation pathway of MTZ, theoretical density functional theory (DFT) calculations were adopted to predict intermediates and degradation pathways of MTZ through Gaussian 09 software equipped at the B3LYP/6-311G(d) level. 34 For the DFT reactivity descriptor calculations, the Fukui function is an important concept in conceptual density functional theory, which has been widely used in the prediction of the reactive site of electrophilic, nucleophilic, and radical attacks. Fukui function is defined as…”

Experimental Photodegradation of OPs and CBs by Advanced Oxidation Techniques in the Aqueous TiO2 Suspensions

“…Theoretical studies were also carried out for all molecules studied. Theoretical work has been published for six molecules other than Phosmet [17] Experimental and theoretical results have been published for Phosmet (OP1), one of the seven pesticides studied [13]. When the theoretical results in these two published articles and the experimental results in this study are examined: At the theoretical stage, the molecule that will enter the reaction most voluntarily, that is, the molecule that requires the lowest energy, is Temephos from organophosphorus pesticides and Methiocarb from the group of carbamate pesticides.…”

Theoretical Study on Reaction Pathways of Methyl Radical with Ethylamine

“…Các tính toán hóa lượng tử trong nghiên cứu này được thực hiện bằng chương trình GAUSSIAN 09 [15]. Lý thuyết phiếm hàm mật độ được sử dụng cho các tính toán này vì nó có thể xử lý tốt về độ nhiễu spin đối với các cấu trúc có các electron độc thân trong hệ phản ứng của gốc methyl với ethylamine [16,17]….. Để tối ưu cấu trúc hình học của các chất phản ứng, trạng thái chuyển tiếp (TS) và sản phẩm chúng tôi đã sử dụng các hàm lai hóa B3LYP dựa trên hàm trao đổi ba thông số của Becke [18][19][20] và hàm tương quan của Yang và cộng sự [21]. Bộ hàm cơ sở của Pople 6-311++G(3df,2p) được áp dụng cho các tính toán này [22].…”