• Bulletin of the Korean Chemical Society
• /
• 제6권1호
• /
• pp.23-29
• /
• 1985

The charge-transfer complexing properties of 1-methyl nicotinamide (MNA), an acceptor, and adenine, a donor, were investigated in water and SDS micellar solutions in relation to the intramolecular interaction in nicotinamide adenine dinucleotide ($NAD^+$). The spectral and thermodynamic parameters of MNA-indole and methyl viologen-adenine complex formations were determined, and the data were utilized to evaluate the charge-transfer abilities of MNA and adenine. The electron affinity of nicotinamide was estimated to be 0.28 eV from charge-transfer energy $of{\sim}300$ nm for MNA-indole. The large enhancement of MNA-indole complexation in SDS solutions by entropy effect was attributed to hydrophobic nature of indole. The complex between adenine and methyl viologen showed an absorption band peaked near 360 nm. The ionization potential of adenine was evaluated to be 8.28 eV from this. The much smaller enhancement of charge-transfer interaction involving adenine than that of indole in SDS solutions was attributed to weaker hydrophobic nature of the donor. The charge-transfer energy of 4.41 eV (280 nm) was estimated for nicotinamide-adenine complex. The spectral behaviors of $NAD^+$ were accounted to the presence of intramolecular interaction in $NAD^+$, which is only slightly enhanced in SDS solutions. The replacement of nicotinamide-adenine interaction in $NAD^+$ by intermolecular nicotinamide-indole interaction in enzyme bound $NAD^+$, and guiding role of adenine moiety in $NAD^+$ were discussed.

• Applied Biological Chemistry
• /
• 제17권2호
• /
• pp.143-148
• /
• 1974

Aflatoxin $B_1$은 전자수용성(電子受容性)을 높여주는 염화아연(鹽化亞鉛) 존재하(存在下)에서 전자공여성분자(電子供與性分子)인 Benzene과 Charge-transfer Complex를 만들며, 그 생성기구(生成機構)는 Aflatoxin $B_1$이 염화아연(鹽化亞鉛)과 일차적(一次的)으로 배위결합(配位結合)된 화합물(化合物)을 거쳐, 이것이 Benzene과 결합(結合)하여 착물(錯物)을 형성(形成)한다. 이 착물(錯物)의 안정도상수(安定度常數) 즉(卽) 평형상수(平衡常數) 0.198 l/mole이었다. 따라서 Aflatoxin $B_1$은 약(弱)한 전자수용체(電子受容體)이나, Benzene 보다 강(强)한 전자공여체(電子供與體)와는 염화아연(鹽化亞鉛)이 존재(存在)하지 않아도 Charge-transfer Complex를 만들 수 있다는 가능성(可能性)을 제시(提示)해 주는 것이며, Tryptophane, Histidine과 같은 강(强)한 전자공여체(電子供與體)를 함유(含有)한 단백질(蛋白質) 또는 Guanine, Adenine과 같은 전자공여체(電子供與體)를 함유(含有)한 DNA등(等)과의 Aflatoxin $B_1$의 결합(結合)은 그 결합(結合) Mechanism으로서 Charge-transfer Complex 형성(形成)으로 이루어진다는 추정(推定)을 할 수 있다.

• Bulletin of the Korean Chemical Society
• /
• 제33권10호
• /
• pp.3448-3450
• /
• 2012

• Bulletin of the Korean Chemical Society
• /
• 제28권4호
• /
• pp.607-612
• /
• 2007

Relationship between charge transfer mechanism and quantum coherence has been investigated using a realtime quantum dynamics approach. In the on-the-fly filtered propagator functional path integral simulation, by separating paths that belong to different mechanisms and by integrating contributions of correspondingly sorted paths, it was possible to accurately obtain quantitative contribution of different transport mechanisms. For a 5'-GAGGG-3' DNA sequence, we analyze charge transfer processes quantitatively such that the governing mechanism alters from coherent to incoherent charge transfer with respect to the friction strength arising from dissipative environments. Although the short DNA sequence requires substantially strong dissipation for completely incoherent hopping transfer mechanism, even a weak system-environment interaction markedly destroys the coherence within the quantum mechanical system and the charge transfer dynamics becomes incoherent to some degree. Based on the forward-backward path deviation analysis, the coherence variation depending on the environment is investigated numerically.

• Bulletin of the Korean Chemical Society
• /
• 제5권3호
• /
• pp.121-126
• /
• 1984

The charge transfer complex formations between indole derivatives and methylviologen were investigated spectroscopically. In aqueous solutions near room temperature, the order of complex stability was tryptamine < tryptophan < indole < indole acetate, which is the reverse order of the magnitude of molar absorptivities. This was interpreted as involvement of contact charge transfer. The decrease of enthalpy of complex formation (-${\Delta}$H) was highest in tryptamine, and lowest in indole acetate. ${\Delta}$H and entropy of complex formation (${Delta}$S) varied nearly in a linear fashion with isokinetic temperature $242^{\circ}$K. These results were attributed to the hydration-dehydration properties of the side chains in indole derivatives. Except indole acetate, the complex formations were greatly enhanced by the addition of sodium dodecyl sulfate(SDS). However, the direct relationship between the enhanced complex formation and SDS micelle formation was not found. The enhanced charge transfer interaction inSDS solutions was attributed to the increased ${\Delta}$S by interaction between methylviologen and SDS in premicellar level. The order of complex stability in SDS solutions was indole acetate < tryptophan < trypamine < indole, which reflects the hydrophobicity of indole derivatives as well as electrostatic interaction between indole derivatives and methylviologen associated with SDS.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
• /
• pp.186.1-186.1
• /
• 2014

Graphene, which is a 2-dimensional carbon material, has been attracting much interest due to its unique properties and potential applications. So far, many interesting experimental and theoretical works have been done concerning the electronic properties of graphene on various substrates. Especially, there are many experimental reports about doping in graphene which is caused by interaction between graphene and its supporting substrates. Here, we report the study of charge transfer between graphene and oxide substrates using density functional theory (DFT) calculations. In this study, we have investigated the charge transfer related with graphene considering various oxide substrates such as SiO2(0001) and MgO(111). Details in charge transfer between graphene and oxides are analyzed in terms of charge density difference, band structure and work function.

• Bulletin of the Korean Chemical Society
• /
• 제35권5호
• /
• pp.1541-1544
• /
• 2014

• Bulletin of the Korean Chemical Society
• /
• 제35권9호
• /
• pp.2851-2854
• /
• 2014

• Bulletin of the Korean Chemical Society
• /
• 제2권1호
• /
• pp.8-11
• /
• 1981

A new potential function based on spectroscopic results for diatomic molecules is presented and applied to the hydrogen bonding systems. The potential energy of interaction is supposed to have electrostatic, polarization, dispersion, repulsion and effective charge-transfer contributions. Estimates of the effective charge-transfer quantity have been made based on the average charge of the proton donor and the acceptor atoms. For dimers such as water, methanol, acetic acid and formic acid, the vibrational stretching frequencies and dimerization energies are calculated and dicussed in connection with Badger-Bauer rule.

• Bulletin of the Korean Chemical Society
• /
• 제12권5호
• /
• pp.574-582
• /
• 1991

The CO molecules adsorbed on Ni(111) surface is studied in the cluster approximation employing EH method with self-consistent charge iteration. The effect of CO coverage is simulated by allowing the variation of valence state ionization potentials of each Ni atom in model cluster according to the self-consistent charge iteration method. The CO coverage dependent C-O stretching frequency shift, adsorption site conversion, and metal work function change are attributed to the charge transfer between metal surface and adsorbate. For CO/Ni(111) system, net charge transfer from Ni surface to chemisorbed CO molecules makes surface Ni atoms be more positive with increasing coverage, and lowers Ni surface valence band. This leads to a weaker interaction between metal surface valence band and Co $2{\pi}^{\ast}$ MO, less charge transfer to a single CO molecule, and the bule shift of C-O stretching frequency. Further increase of coverage induces the conversion of 3-fold site CO to lower coordination site CO as well as the blue shift of C-O stretching frequency. This whole process is accompanied by the continuous increase of metal work function.