Tailor-made agarose-based reactive beads for hemoperfusion and plasma perfusion

Composite beads of approximately 1mm diameter, made of cross-linked agarose and containing Fuller’s Earth or zirconium oxide powders, were prepared and used in extracorporeal systems for blood detoxification. The former was used for the removal of Paraquat, while the latter was used to remove inorganic phosphate from hyper-phosphatamic animals with or without acute renal failure. The high surface area of the powder, combined with the low resistance to diffusion in the cross-linked agarose matrix, are highly advantageous. The crosslinking provides high mechanical strength, heat stability, prolonged shelf life, good blood flow characteristics, and prevents the release of fine particles into the blood. Crosslinked agarose beads of 1 mm diameter, containing chemically-bound heparin were also prepared, and used as a model for direct contact removal of LDL-cholesterol from the blood of familial hypercholesterolemic patients by hemoperfusion. The high capacity of these beads (over 5 mg LDL/mL beads) indicates that this clinical modality can replace the highly expensive plasmapheresis procedure presently used.     

Energy spectra of the ocean's internal wave field: theory and observations

The high-frequency limit of the Garrett and Munk spectrum of internal waves in the ocean and the observed deviations from it are shown to form a pattern consistent with the predictions of wave turbulence theory. In particular, the high-frequency limit of the Garrett and Munk spectrum constitutes an exact steady-state solution of the corresponding kinetic equation.     

A linear programming approach to water-resources optimization

A linear-programming model for use in analysis and planning of multiobjective water resources systems is described in this paper. A typical system consists of reservoirs, hydropower stations, irrigated land, artificial and navigation channels, etc., over a reach of a river or a river basin.The linear programming approach is studied and compared with other approaches: mixed integer-linear dynamic and nonlinear. The advantages and drawbacks of its use in a real case-study are also described.     

Temperature-induced conformational changes in turtle myoglobin

Summary A sea turtle myoglobin has been spin labelled in the cyanomet form (MbT-CN) with a maleimide spin label and temperature-induced changes were monitored by EPR. The EPR spectrum is composed by an immobilized and a more mobile signal. Comparison of this spectrum with spectra obtained from other proteins, blocking of the NH₂-terminal and titration of SH groups lead to the conclusion that a reactive histidine is involved in the spin labelling. Our results on the temperature-induced changes monitored by the maleimide spin label suggest that a sequence of events is taking place in the transition which leads to protein denaturation (predenaturation): with increase in temperature atpH 8.5 the EPR parameter for the immobilized signal (α _EPR) is the first to report the structural change (T _1/2=28°C); then the mobile signal changes (T _1/2=44°C) and finally the active centre monitored by optical absorption of the iron heme undergoes these changes (T _1/2=64°C). The activation energy calculated from the mobile spectrum is around 3 kcal/mol showing that these changes are quite subtle if compared to the enthalpy changes monitored by optical absorption of iron (40 kcal/mol). This predenaturation occurring in the range (30÷50)°C seems to be a general property of myoglobins, as has been observed also for whale and applysia.

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Riassunto La mioglobina di tartaruga marina è state marcata con spin label maleimida nella forma cianometa (MbT-CN) e cambiamenti di temperatura sono stati indotti e accompagnati per EPR. Lo spettro di EPR è composto da un segnale fisso e un’altro piú mobile. Comparazioni di questo spettro con altri ottenuti da altre proteine, bloccando l’NH₂ terminale e titolando il gruppo SH, mettono in evidenza che un’istidina reattiva partecipa alla marcazione dello spin label. I nostri risultati nei cambiamenti di temperatura indotti e accompagnati dallo spin label indicano che la sequenza di fatti ha indotto una transizione che porta alla denaturazione della proteina (predenaturazione): con aumento della temperature apH=8.5, il parametro di EPR per il segnale fisso (α _EPR) è il primo a rivelare il cambiamento strutturale (T _1/2=28°C), allora il segnale mobile si modifica (T _1/2=44°C) e infine il centro attivo accompagnato per l’assorbimento ottico del ferro subisce questo cambiamento (T _1/2=64°C). L’energia di attivazione calcolata per lo spettro mobile è intorno di 3 kcal/mol indicando che questo cambiamento è piccolo quando comparato con la variazione di entalpia ottenuta per l’assorbimento ottico del ferro (40 kcal/mol). Questa predenaturazione che avviene nella fascia da 30 a 50°C sembra essere una proprietà comune delle mioglobine, come è stato osservato anche per la mioglobina di balena e di aplisia.

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Резюме В миоглобин морской черепахи вводится спиновая метка в форму (MbT-CN) и методом EPR контролируются термоиндуцированиые изменения. Спектр EPR составляют неподвижные и более подвижные сигналы. Сравнение этого спектра со спектрами других белков, блокирование концевой NH₂-группы и титрование SH-групп приводит к выводу, что помечены активные гистидины. Наши результаты по наблюдению за термоиндуцированными изменениями дают возмож-ность предположить, что имеет место последовательность событий в процессе перехода, который приводит к денатурации белка (пред-денатурация): с увеличением температуры приpH=8.5 параметр EPR для неподвижного сигнала (α _EPR) первым регистрирует структурное изменение (T _1/2=28°C); затем изменяется подвижный сигнал (T _1/2=44°C) и, наконец, претерпевает изменения активный центр, который мониторируется за счет оптического поглощения в железе (T _1/2=64°C). Энергия активации, вычисленная на основе подвижного спектра, составляет примерно 3 ккал/моль. Это указывает на то, что указанные изменения являются весьма тонкими по свавнению с изменениями энтальпии, которая мониторируется за счет оптического поглощения в железе (40 ккал/моль). Эти явление пред-денатурации, которое наблюдается в области (30÷50)°C, по видимому, представляет общее свойство миоглобинов.

     

The molecular aggregation of pyronin Y in natural bentonite clay suspension

The molecular aggregation and spectroscopic properties of Pyronin Y (PyY) in the suspension containing natural bentonite clay were studied using molecular absorption, steady-state and time-resolved fluorescence spectroscopy techniques. Interaction between the clay particles and the cationic dye compounds in aqueous solution resulted in significant changes in spectral properties of PyY compared to its molecular behavior in deionized water at the same concentration. These changes were due to the formation of dimer and aggregate of PyY in the clay suspension as well as the presence of the dye monomer. The H-type aggregates of PyY in the clay suspension were identified by the observation of a blue-shifted absorption band of the dye compared to that of its monomer. In spite of diluted dye concentrations, the H-aggregate of PyY in the clay suspension was formed. The intensive aggregation in the clay suspension attributed to the localized high dye concentration on the negatively charged clay surfaces. Adsorption sites of PyY on the clay particles were discussed by deconvulated absorption and excitation spectra. Fluorescence spectroscopy studies revealed that the fluorescence intensity of PyY in the clay suspension is decreased by H-aggregates drastically. Moreover, the presence of H-aggregates in the clay suspension resulted in the decrease of fluorescence lifetime and quantum yield of PyY compared to those in deionized water.     

Simple waves do not avoid eigenvalue crossings

General one‐parameter families of matrices avoid eigenvalue crossings. It is shown that the matrices associated with the simple waves of nonlinear systems of conservation laws do not obey this rule: a subset of simple waves with nonzero measure has crossing eigenvalues. © 2009 Wiley Periodicals, Inc.     

Principal Dynamical Components

A procedure is proposed for a dimension reduction in time series. Similarly to principal components, the procedure seeks a low‐dimensional manifold that minimizes information loss. Unlike principal components, however, the procedure involves dynamical considerations through the proposal of a predictive dynamical model in the reduced manifold. Hence the minimization of the uncertainty is not only over the choice of a reduced manifold, as in principal components, but also over the parameters of the dynamical model, as in autoregressive analysis and principal interaction patterns. Further generalizations are provided to nonautonomous and non‐Markovian scenarios, which are then applied to historical sea‐surface temperature data. © 2012 Wiley Periodicals, Inc.     

On difference sets in high exponent 2-groups

We investigate the existence of difference sets in particular 2-groups. Being aware of the famous necessary conditions derived from Turyn’s and Ma’s theorems, we develop a new method to cover necessary conditions for the existence of (2^2d+2,2^2d+1?2 ^d ,2^2d ?2 ^d ) difference sets, for some large classes of 2-groups. If a 2-group G possesses a normal cyclic subgroup 〈x〉 of order greater than 2 ^d+3+p , where the outer elements act on the cyclic subgroup similarly as in the dihedral, semidihedral, quaternion or modular groups and 2 ^p describes the size of G′∩〈x〉 or C _G (x)′∩〈x〉, then there is no difference set in such a group. Technically, we use a simple fact on how sums of 2 ⁿ -roots of unity can be annulated and use it to characterize properties of norm invariance (prescribed norm). This approach gives necessary conditions when a linear combination of 2 ⁿ -roots of unity remains unchanged under homomorphism actions in the sense of the norm.