Conformationally resolved spectroscopy of jet-cooled methacetin

Moon, C.J.,Ahn, A.,Min, A.,Seong, Y.G.,Kim, J.H.,Choi, M.Y. North Holland 2017 Chemical physics letters Vol.688 No.-

<P>The excitation spectra of jet-cooled methacetin (MA) have been measured using a combination of massselected resonant two-photon ionization and ultraviolet-ultraviolet hole-burning (UV-UV HB) spectroscopy in the gas phase. Four different UV-UV HB spectra originating from two conformers of MA (syn-and anti-MA) with their fundamental and hot transitions have been obtained. IR-dip spectroscopy has conclusively confirmed the coexistence of the two conformers with the aid of theoretical calculations. Vibronic band assignments in the low frequency region caused by internal methyl group rotation in the methyl-capped peptide group, which originate from the 1e rotational level, are presented. (C) 2017 Elsevier B.V. All rights reserved.</P>

Combining electrochemical, surface topography analysis, and theoretical calculation methods to insight into the anti-corrosion property of Syzygium samarangense leaf extract

Yang Zhou,Chong Zhu,Shenying Xu,Bin Xiang,Riadh Marzouki 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.102 No.-

The anti-corrosion ability of Syzygium samarangense leaf extract (SSLE) was studied using electrochemicalways, topography research and theoretical calculations. The results of electrochemical tests indicatedthat SSLE can effectually control the Q235 steel corrosion in sulfuric acid environment. When the concentrationof SSLE was 400 mg/L, its anti-corrosion ability can be close to 90%. SSLE can efficaciously restrictthe cathodic and anodic reactions, and can still emerge high corrosion inhibition character at a certaintemperatures scope. The surface morphology test shows that the Q235 steel becomes smooth and brightafter adding SSLE. Theoretical calculation data indicated that SSLE can manifest high corrosion inhibitionperformance. The adsorption of SSLE at the solution/surfaces of steel accords with the Langmuir adsorptionmodel.

양자화학적 계산에 의한 올리고펩티드 수화물의 구조분석

심재호(Jae-Ho Sim) 한국산학기술학회 2018 한국산학기술학회논문지 Vol.19 No.7

이성질체의 형태는 수용액 상태에서 종종 안정성과 반응성 등의 기본상태 뿐만 아니라 사슬성장 및 접힘 과정으로 인하여 형태형성에 영향을 주기 때문에 올리고펩티드의 형태를 이해하는 것이 중요하다. 본 논문에서는 L-알라닌(LA), 글리신(G) 5량체 모델의 무수 및 수화물(수화율; h/1) 상태의 구조와 에너지를 4가지 형태이성질체 (베타-확장형;= t-/t+, PPII형; g-/t+, PPII-유사형; g-/g+ 및 알파-나선형; g-/g-)에 대하여 B3LYP/6-31G(d,p)를 이용하여 양자화학계산(QCC) 방법으로 분석하였다. 구조최적화는 밀도함수 이론(DFT)으로써 B3LYP를 사용하였으며, 기본설정(Basic set)으로는 6-31G(d,p)를 이용하였다. 이미노 양성자(NH)를 갖는 LA와 G에서 베타-확장형, PPII-유사형, 알파-나선형의 3가지 형태가 얻어졌으며, 대부분 물 분자가 PPII-유사형과 알파-나선형에서는 CO-HN 분자 내 수소결합 사이에 주로 삽입되었고, 베타-확장형은 CO기에 부착되었다. 또한, LA와 G에서 PPII-유사형 형태이성질체가 무수 및 수화물 상태에서 가장 안정적이었으며, PPII 형태이성질체는 얻어지지 않았다. LA에 대한 결과는 알라닌 올리고펩티드의 안정적인 형태가 주로 PPII라고 보고한 다른 연구의 실험적 및 이론적인 결과와는 상이했다. 올리고펩티드 형태이성질체의 생성패턴과 안정성이 CO-HN의 분자 내 수소결합의 존재 여부 또는 출발 아미노산 내 NH2기의 존재 여부에 강한 영향을 받는 것을 알 수 있었다. The structures and energies of the anhydrate and hydrate (hydrate rate: h of 1) states of L-alanine (LA) and glycine (G) were calculated by quantum chemical calculations (QCCs) using B3LYP/6-31G(d,p) for four types of conformers (β-extended: φ/ψ = t-/t+, PPII: g-/t+, PPII-like: g-/g+, and α-helix: g-/g-). In LA and G, which have an imino proton (NH), three conformation types of β-extended, PPII-like, and α-helix were obtained, and water molecules were inserted mainly between the intra-molecular hydrogen bond of CO···HN in PPII-like and α-helix, and attached to the CO group in β-extended. In LA and G, PPII-like conformers were most stable in the anhydrate and hydrate states, and the result for LA was different from some experimental and theoretical results from other studies reporting that the main stable conformation of alanine oligopeptide was PPII. The formation pattern and stability of the conformation of the oligopeptide was strongly dominated by the presence/absence of intra-molecular hydrogen bonding of CO···HN, or the presence/absence of an NH2 group in the starting amino acid.

Synthesis, Characterization and Quantum Chemical Studies on a Novel Cobalt(II) 1,2,3,4-Tetra-(4-pyridyl)-thiophene Coordination Polymer

Lin, Jian-Guo,Qiu, Ling,Meng, Qing-Jin Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.1

Studies on the Different Reaction Pathways between 3-Acetyl-5-benzoyl-6-methyl-2-phenyl-4H-pyran-4-one and Alkylamines

Genc, Hasan,Tan, Meltem,Gumus, Selcuk,Menges, Nurettin,Bildirici, Ishak,Sener, Ahmet Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.9

3-Acetyl-5-benzoyl-6-methyl-2-phenyl-4H-pyran-4-one has been subjected to condensation with a series of primary amines (ethylamine - octylamine) to clarify the proposed mechanism in our previous study. The reactions of the shorter amines of the series (ethylamine - butylamine) yielded unsymmetric pyridinone products, whereas the other amines (pentylamine - octylamine) yielded symmetrical pyridinones. The starting material and the products as well as the intermediates have been subjected to theoretical analysis by quantum chemical calculations at B3LYP/6-31G(d,p) level, which provided supporting data for the experimental findings.

Studies on the Different Reaction Pathways between 3-Acetyl-5-benzoyl-6-methyl-2-phenyl-4H-pyran-4-one and Alkylamines

Kwang Yeon Hwang,Meltem Tan,Selçuk Gümüş,Nurettin Mengeş,İshak Bildirici,Ahmet Şener 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.9

3-Acetyl-5-benzoyl-6-methyl-2-phenyl-4H-pyran-4-one has been subjected to condensation with a series of primary amines (ethylamine – octylamine) to clarify the proposed mechanism in our previous study. The reactions of the shorter amines of the series (ethylamine – butylamine) yielded unsymmetric pyridinone products, whereas the other amines (pentylamine – octylamine) yielded symmetrical pyridinones. The starting material and the products as well as the intermediates have been subjected to theoretical analysis by quantum chemical calculations at B3LYP/6-31G(d,p)level, which provided supporting data for the experimental findings.

Comparison of Structural Types of Proline Pentamer by Quantum Chemical Calculation (QCC)

심재호 국제문화기술진흥원 2023 International Journal of Advanced Culture Technolo Vol.11 No.2

In this study, Proline pentamer model was used to investigate change in the dihedral angle, intramolecular hydrogen bonding and formation energies during structural optimization. L-Proline (LP, as an imino acid residue) pentamers having four conformation types [β: φ/ψ=t−/t+, α: φ/ψ=g−/g−, PPII: φ/ψ=g−/t+ and P-like: φ/ψ= g−/g+] were carried out by QCC [B3LYP/6-31G(d,p)]. The optimized structure and formation energy were examined for designated structure. In LP, P-like and PPII types did not change by optimization, and β types were transformed into PPII having no H-bond independently of the designated ψ values. PPII was more stable than P-like by about 2.2 kcal/mol/mu. The hydrogen bond distances of d2(4-6) type H-bonds were 1.94 - 2.00Å. In order to understand the processes of the transformations, the changes of φ/ψ, distances of NH-OC (dNH/CO) and formation energies (ΔE, kcal/mol/mu) were examined.

Synthesis, Characterization and Quantum Chemical Studies on a Novel Cobalt(II) 1,2,3,4-Tetra-(4-pyridyl)-thiophene Coordination Polymer

Jian-Guo Lin,Ling Qiu,Qing-Jin Meng 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.1

Comparison of Structural Types of L-Alanine Pentamer by Quantum Chemical Calculation

Kobayashi Minoru,심재호 한국공업화학회 2022 공업화학 Vol.33 No.4

L-alanine (LA, as an amino acid residue) pentamer model was used to investigate changes in the dihedral angle, intramolecular hydrogen bonding and formation energies during structural optimization. LA pentamers having four conformation types [β: φ/ψ=t−/t+, α: φ/ψ=g−/g−, PPII: φ/ψ=g−/t+ and P-like: φ/ψ= g−/g+] were carried out by quantum chemical calculations (QCC) [B3LYP/6-31G(d,p)]. In LA, β, α, and P-like types did not change by optimization, having an intra-molecular hydrogen bond: NH···OC (H-bond), and PPII types in the absence of H-bond were transformed into P-like at the designated ψ of 140°, and to β at that of 160° or 175°. P-like and α were about 0.5 kcal/mol/mu more stable than β. In order to understand the processes of the transformations, the changes of φ/ψ, distances of NH-OC (dNH/CO) and formation energies (ΔE, kcal/mol/mu) were examined.

알라닌 올리고머의 배좌구조에 관한 양자화학적 계산

심재호(Sim, Jae-Ho) 한국산학기술학회 2015 한국산학기술학회논문지 Vol.16 No.2

본 연구는 올리고펩티드의 연쇄성장 과정에서의 배좌의 변화를 조사하기 위하여 알라닌 올리고머 모델의 2량체 부터 5량체 까지 양자화학 계산(QCC)에 의한 구조최적화 계산을 하였다. 말단기의 영향을 확인하기 위하여 N말단 및 C말단이 공히 amide 구조를 갖는 “amide type” (CH,₃CONH-and-CONHCH₃)과 N말단만이 methyl 구조를 갖는 “methyl type” (CH₃NH-and-CONHCH₃)의 2종류 모델을 준비하였다. 5량체 까지의 구조 최적화 계산 결과 3종류의 형태이성질체로 수렴이 되었다. 안정성이 높은 순서로 각각 α 나선형, PPII 유사형, β 확장형으로 나타났으며, 사슬회전 방향이 서로 반대인 형태이성 질체간의 에너지 값은 동일하게 나타났다 (5량체, “amide type” 좌?우회전형: ΔE=-1.05, “methyl type” 좌?우회전형: Δ E=-1.62). α 나선형의 모노머 단위당 에너지변화(ΔE)는 모노머의 증가와 함께 감소하였다. Conformational change during chain propagation of alanine oligomer was investigated by quantum chemical calculation(QCC) using 2∼5mers(×=2∼5) models. For estimation of the end group effects, two types of end group. “amide type”(CH₃CONH- and -CONHCH₃) and “methyl type” (CH₃NH- and -CONHCH₃), were prepared as both ends(N-and-C). Conformers optimized for 5-mer converged to three types of φ/Ψ : α-helix(g+/g+, or g-/g-), PPII-like(extended helix-like, g+/g-, or g-/g+), and β-extended (t+/t-, or t-/t+), in the order of lower energy, and the energies of left- and right- handed conformers were the same (5-mer. amide type ΔE= -1.05, right type ΔE= -1.62). Energies of the monomer unit(ΔE) of α-helix decreased with increases of monomer.