Assignment of conformation-sensitive near-infrared bands in high-spin ferrous haemoproteins. Low-temperature magnetic circular dichroism data

An assignment of the near-infrared bands in the 600–800 nm spectral region observed in magnetic circular dichroism (MCD) spectra of high-spin ferrous haemoproteins is presented. The assignment is based on a relative energy level scheme for iron d-electrons, a comparison of predicted and measured temperature dependences of MCD intensity, a sign of MCD bands and a group theoretical analysis of allowed transitions. The proposed assignment is consistent with the ∼15-nm red shift of the ∼760 nm band on breakage of the Fe-His bond in deoxy-myoglobin at low pH, with low-temperature photolysis experiments available for CO complexes of several haemoproteins. In accordance with the observations, the intensity of the MCD bands for proteins with a sulphur anion of cysteine as proximal haemligand (cytochrome P450 and chloroperoxidase) is predicted to be diminished by at least one order of magnitude compared to that for proteins with an imidazole of a histidine as a protein-derived haemligand (i.e. myoglobin, haemoglobin and horseradish peroxidase). Received: 4 February 1997 / Accepted: 1 May 1997     

Sorption of carbon dioxide by the composite sorbent “potassium carbonate in porous matrix”

Sorption of CO₂ in the presence of water vapor by the K₂CO₃—-Al₂O₃ composite sorbent was studied by IR spectroscopy in situ, X-ray diffraction analysis, and the differentiating dissolution method and reasons for a decrease in its dynamic capacity are given. The samples containing K₂CO₃·1.5H₂O in pores are characterized by the maximal dynamic capacity. A mechanism for CO₂ sorption was proposed, which qualitatively explains the obtained dependence of the capacity on the water content in the composite sorbent. A high dynamic capacity can be maintained by regeneration of the sorbents by water vapor at 170 °N. The capacity of the sorbents decreases during the first 10 sorption—regeneration cycles due to the formation of an inactive phase of potassium aluminum carbonate.     

Comparative study of photodynamic properties of 13,15-N-cycloimide derivatives of chlorin p6

Comparative study of 13,15-[N-(2-hydroxyethyl)]cycloimide chlorin p6 (2), 13,15-(N-acetoxy)cycloimide chlorin p6 (3), 13,15-(N-hydroxy)cycloimide chlorin p6 methyl ester (4) and 13,15-(N-methoxy)cycloimide chlorin p6 methyl ester (5) together with the previously investigated 13,15-[N-(3-hydroxypropyl)]cycloimide chlorin p6 (1) was performed. The dependence of the key photodynamic properties of 1-5 on the introduced substituents was analyzed. The photoinduced cell-killing activity of 4 is 100- and 280-fold higher than that of chlorin p6 and Photogem, respectively, as estimated on A549 human lung adenocarcinoma cells. The activity is reduced eight times in the order 4 > 5 > 1 > 2 > 3. The intracellular accumulation of 1-5 occurs in cytoplasm in a monomeric form bound to the lipids of cellular membranes. This form of 1, 2, 3, 4 and 5 is characterized by the high quantum yield of singlet oxygen generation, which depends on the introduced substituents, 0.66, 0.59, 0.35, 0.51 and 0.73, respectively. The photostability is two-fold less for 1 and four-fold less for 2, 3 and 5 than for 4. The rates of cellular uptake and efflux of 1-5 vary widely, thus providing the way to optimize the pharmacological properties of the photosensitizer (PS) using the respective substituents. Modifying the substituents, 1-5 were targeted to different cellular organelles. The enhanced accumulation in the Golgi apparatus and mitochondria complemented with diffuse staining of intracellular membranous structures is a property of 1-4. Compound 5 accumulates selectively in the lipid droplets and stains weakly perinuclear structures. Temperature-sensitive mechanisms of transport are responsible for the 1-4 uptake. Diffusion can play a role in the internalization of 5 but not of 1-4. Endocytosis via caveolae, clathrin-dependent and adenosine triphosphate-dependent pathways are not noticeably involved in the 1-5 internalization. Independently from their intracellular localization 1, 4 and 5 are highly efficient near-IR PS, which induce predominantly an apoptotic type of cell death under conditions providing ca 50% level of phototoxicity and necrosis at the 100% level of phototoxicity.     

Near-infrared laser operation of Cr3+ centers in chromium-doped LiInGeO4 and LiScGeO4 crystals

Laser action has been demonstrated in two new tunable Cr3+-doped crystals. Absorption, emission, and excitation measurements for various crystal orientations have been performed for chromium-doped LiInGeO4 and LiScGeO4 single crystals. From the spectroscopic measurements, two optical active centers were identified: tetrahedrally coordinated Cr4+ and octahedrally coordinated Cr3+. Gain-switched, tunable laser operation of Cr3+ centers has been demonstrated in both crystals. An ultrawide tuning range from 1150 to 1480 nm for LiInGeO4 and 1220-1380 nm for LiScGeO4 has been achieved. To our knowledge this is the widest bandwidth and the most near-infrared shifted wavelength range for lasing ever demonstrated for Cr3+ ions.     

The thermodynamic characteristics of acetone adsorption on Raney nickel under liquid phase hydrogenation conditions

An adsorption-calorimetric study was performed to determine the thermodynamic characteristics of adsorption of acetone on Raney nickel from aqueous solutions of 2-propanol of various compositions directly during liquid-phase hydrogenation. At adsorbate concentrations below 3 × 10⁻³ M, adsorption occurred by the mechanism of the filling of the pore volume of the catalyst with saturated solutions of complex compositions. At higher concentrations, the process followed the mechanism of condensation interactions. Two-dimensional phase diagrams were obtained for Raney nickel surface layers involved in the adsorption of acetone. These diagrams substantiated the possibility of two-dimensional phase transitions in adsorption solutions.     

Blind dereverberation in the deep sea

Experimental data are presented on the blind dereverberation of the noise-type signal generated by a sound source moving in the deep sea. The noise emitted by a towed source is received by a drifting hydrophone with a high excess of the signal over the ambient noise, which results in a stable interference pattern of high contrast. The observed interference structure indicates that the signal arrives at the receiver along different paths. With the use of the blind dereverberation technique for the signal processing and without any a priori information on the properties of the propagation channel, the parameters (the delay, the amplitude, and the phase) of each of the seven interfering signals are determined. From the data obtained, the frequency response of the filter that provides a strong suppression of the reverberation is calculated and the spectrum of the received signal is obtained without any interference distortions.     

Application of isograms in the search for inference

Translated from Issledovaniya po Prikladnoi Matematike, No. 1, pp. 94–102, 1973.     

Orbit–orbit interaction in the NO–Fe(II)Hemoproteins studied by the low-temperature magnetic circular dichroism: Dynamic Jahn–Teller effect detected by MCD

This paper analyzes the low-temperature magnetic circular dichroism of NO–Fe(II)hemoproteins in detail. We include the Jahn–Teller effect in our consideration of the low-temperature MCD results.