Inclusion complexes of proteins: Interaction of cyclodextrins with peptides containing aromatic amino acids studied by competitive spectrophotometry

The stability constants were measured of inclusion complexes formed from aromatic amino acids and their oligopeptides with - and-cyclodextrin, hydroxypropyl-cyclodextrin, and partially methylated-cyclodextrin. The method of competitive spectrophotometry withp-nitrophenol as a competing reagent was used, and measurements were made at pH 7.4-Cyclodextrin formed complexes of higher stability than the other hosts. The stability of complexes of oligopeptides containing L-phenylalanine was invariably higher than that of L-phenylalanine itself. A model for interaction of proteins with cyclodextrins is proposed, in which the most stable complexes are formed when the native functional form of proteins is unfolded and the nonpolar residues that are buried inside the structure are exposed to water. The complexation of the unfolded structure favors its formation; thus thermal denaturation of proteins is easier in the presence of cyclodextrins. On the other hand, this complexation prevents the intermolecular association of unfolded structures by noncovalent hydrophobic bonding between the exposed nonpolar residues; furthermore, the unfolded complexed forms may revert to the native functional form. This prevention of intermolecular association may explain the stabilizing effect of cyclodextrins on solutions of proteins: a return to the native form is achieved more easily from the complexed, unfolded form than from the unfolded, aggregated forms.Dedicated to Professor József Szejtli.     

Simultaneous recording of spin-state-selective NMR spectra for different InS spin systems

Heteronuclear magnetization transfer occurring during heteronuclear cross-polarization mixing processes in liquid-state NMR experiments can be easily monitored as a function of the involved in-phase, antiphase, and multiple-quantum magnetization components. The theoretical background on the simultaneous detection of E.COSY-type, TROSY-type, or spin-edited multiplet patterns for different IS and I(2)S spin systems in the same solution-state NMR spectrum is described. The proposed pulse scheme preserves high sensitivity levels and shows good tolerance to the presence of undesired cross-talk artifacts for both NH and NH(2) multiplicities providing an interesting NMR tool for biomolecular applications.     

Chemie der Seltenerdmetalle, 19. Mitt.: Dissoziation des Ce(III)-succinats im sauren Gebiet

Zusammenfassung Die Dissoziation von Ce₂ Suc ₃·3 H₂O^** in Perchlorsäure-Lösungen wurde verfolgt und die Dissoziationskonstanten der Succinationen: (CeSuc)⁺ und (CeSuc ₂)^– unter Benützung einer Löslichkeitsmethode in 1m-NH₄ClO₄-Lösung bei 25°C bestimmt. Die Löslichkeitsprodukte von Ce₂ Suc ₃: [Ce³⁺]²[Suc ^2–]³, [CeSuc ⁺]²[Suc ^2–], [CeSuc ⁺][CeSuc ₂ ^–] wurden bestimmt.

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The dissociation of Ce₂ Suc ₃·3H₂O in perchloric acid solutions was investigated. The dissociation constants of the succinate ions (CeSuc)⁺ and (CeSuc ₂)^– were determined inM-NH₄ClO₄ at 25° using a solubility method and the solubility products of Ce₂ Suc ₃, i. e. [Ce³⁺]²[Suc ^2–]³, [CeSuc ⁺]²[Suc ^2–], [CeSuc ⁺][CeSuc ₂ ^–] measured.

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18. Mitt.:R. Pastorek, Lanthantartrate im neutralen und alkal. Bereich. Mh. Chem.99, 676 (1968).     

Theory and applications of ion-selective electrodes: Part 6

This review of ion-selective electrodes is arranged in the same way as earlier reviews of this series. The whole subject continues to grow steadily. Considerable attention has been given to clinical analysis of body electrolytes, particularly by means of automatic devices. About 800 papers published between Spring 1983 and Spring 1985 (including several omitted in Part 5) are mentioned, covering the theory of membrane phenomena, technology, fixed-state eletrodes, liquid-membranes electrodes, potentiometric biosensors and miscellaneous systems.     

Spontaneous formation of bags with negative surface energy

We demonstrate within the Ginzburg-Landau model of a confining medium that the surface energy associated with the interface between the normal and the confining phases can be negative, and briefly discuss some consequences of this fact.Dedicated to the memory of M. Gmitro.This work was done at the Niels Bohr Institute Copenhagen, and put into its final form at the Institute of Theoretical Physics, of University of Regensburg. I thank both institutes for their generous hospitality and Professors Poul Olesen and Wolfram Weise for discussions.     

Theory and applications of ion-selective electrodes Part III

This review of ion-selective electrodes is arranged in the same way as Parts I and II. The continuous growth of the whole subject should be noted. Theory has particularly progressed through mechanistic studies. Among new types of electrodes, ISFET systems have become important. Among new applications of both solid and liquid membrane electrodes, the fluoride electrode still predominates, closely followed by potassium electrodes. In the field of biological and medical applications, the steady growth is significant. More than 800 papers published between mid-1976 and the end of 1978 are mentioned in the review.     

Detection of NAD+-dependent alcohol dehydrogenase activities in YR-1 strain of Mucor circinelloides, a potential bioremediator of petroleum contaminated soils

Different soluble NAD⁺-dependent alcohol dehydrogenase (ADH) isozymes were detected in cell-free homogenates from aerobically grown mycelia of YR-1 strain of Mucor circinelloides isolated from petroleumcontaminated soil samples. Depending on the carbon source present in the growth media, multiple NAD⁺-dependent ADHs were detected when hexadecane or decane was used as the sole carbon source in the culture media. ADH activities from aerobically or anaerobically grown mycelium or yeast cells, respectively, were detected when growth medium with glucose added was the sole carbon source; the enzyme activity exhibited optimum pH for the oxidation of different alcohols (methanol, ethanol, and hexadecanol) similar to that of the corresponding aldehyde (≈7.0). Zymogram analysis conducted with partially purified fractions of extracts from aerobic mycelium or anaerobic yeast cells of the YR-1 strain grown in glucose as the sole carbon source indicated the presence of a single NAD⁺-dependent ADH enzyme in each case, and the activity level was higher in the yeast cells. ADH enzyme from mycelium grown in different carbon sources showed high activity using ethanol as substrate, although higher activity was displayed when the cells were grown in hexadecane as the sole carbon source. Zymogram analysis with these extracts showed that this particular strain of M. circinelloides has four different isozymes with ADH activity and, interestingly, one of them, ADH4, was identified also as phenanthrene-diol-dehydrogenase, an enzyme that possibly participates in the aromatic hydrocarbon biodegradation pathway.