Összetett reakciórendszerek egyensúlyi és kinetikai vizsgálata = Equilibrium and kinetic studies of complex chemical systems

A válaszreakciók korábban kidolgozott elméletére alapozva definiáltuk az egyensúlyi csatolás fogalmát. Bemutattuk, hogy - megfelelő körülmények között - szinte törvényszerűen jelentkeznek a Le Chatelier Braun elvnek látszólag ellentmondó jelenségek. Az egyensúlyi csatolás elméletileg megalapozott fogalom, s helyettesitheti a folyamatok egyszerüsitett értelmezéséböl származó, ellentmondásos termodinamikai csatolás fogalmát. Nyolc különböző összetett kinetikai rendszeren végeztünk kinetikai vizsgálatokat, s javasoltunk mechanizmust, amellyekkel számos egzotikus kinetikai jelenség (szuperkatalizis, mintázatképződés, tized-rendű reakció) értelmezhetővé vált. | Based on the theory of response reactions elaborated by us before, we have introduced the concept od equilibrium coupling. It was shown that - under appropriate conditions - the phenomena seemingly in contradiction with the L Catelier Barun principle are almost inevitable in multilple equilibrium systems. The equilibrium coupling is theorethically sound principle and may replace the concept of thermodynamic coupling which is originated from the simplified interpretation of the chemical reactions. Detailed kinetic studies have been carried out in eigth different complex kinetic systems. Based on the experiments appropriate mechanisms are suggested which interpret the different exotic phenomena (super-catalysis, pattern formation, formal reaction order of ten)

On the possible roles of N-terminal His-rich domains of Cu,Zn SODs of some Gram-negative bacteria

The Cu,Zn superoxide dismutases (Cu,Zn SOD) isolated from some Gram-negative bacteria possess a His-rich N-terminal metal binding extension. The N-terminal domain of Haemophilus ducreyi Cu,Zn SOD has been previously proposed to play a copper(II)-, and may be a zinc(II)- chaperoning role under metal ion starvation, and to behave as a temporary (low activity) superoxide dismutating center if copper(II) is available. The N-terminal extension of Cu,Zn SOD from Actinobacillus pleuropneumoniae starts with an analogous sequence (HxDHxH), but contains considerably fewer metal binding sites. In order to study the possibility of the generalization of the above mentioned functions over all Gram-negative bacteria possessing His-rich N-terminal extension, here we report thermodynamic and solution structural analysis of the copper(II) and zinc(II) complexes of a peptide corresponding to the first eight amino acids (HADHDHKK-NH2, L) of the enzyme isolated from A. pleuropneumoniae. In equimolar solutions of Cu(II)/Zn(II) and the peptide the MH2L complexes are dominant in the neutral pH-range. L has extraordinary copper(II) sequestering capacity (KD,Cu = 7.4×10–13 M at pH 7.4), which is provided only by non-amide (side chain) donors. The central ion in CuH2L is coordinated by four nitrogens {NH2,3Nim} in the equatorial plane. In ZnH2L the peptide binds to zinc(II) through a {NH2,2Nim,COO–} donor set, and its zinc binding affinity is relatively modest (KD,Zn = 4.8×10–7 M at pH 7.4). Consequently, the presented data do support a general chaperoning role of the N-terminal His-rich region of Gram-negative bacteria in copper(II) uptake, but do not confirm similar function for zinc(II). Interestingly, the complex CuH2L has very high SOD-like activity, which may further support the multifunctional role of the copper(II)-bound N-terminal His-rich domain of Cu,Zn SODs of Gram-negative bacteria. The proposed structure for the MH2L complexes have been verified by semiempirical quantum chemical calculations (PM6), too

Theoretical characterization of gas-liquid chromatographic molecular stationary phases with quantum chemical descriptors

Quantitative structure-property relationship, (QSPR) solvent model has been developed for the McReynolds constants (prototypical solutes) on 36 gas-liquid chromatographic stationary phases. PM6 semiempirical quantum chemical calculations combined with conductor-like screening model (COSMO) has been utilized. From 276 descriptors considered, forward stepwise variable selection, followed by best subset selection, yielded linear regression models containing six purely quantum chemical and two hybrid, topologically based descriptors. Internal (leave-one-out and bootstrap) as well as external validation methods confirmed the predictive power of these structure-driven models across all 10 McReynolds constants, with 40 Kovats-index units overall root-mean-square prediction error estimate. (c) 2009 Elsevier B.V. All rights reserved