Liposome application: problems and prospects

Liposomes are now in the marketplace as cosmeticeuticals and, more important, pharmaceuticals. Three major achievements of liposome application: steric stabilization, remote loading of drugs by pH and ion gradients, and lipoplexes based on complexes of cationic liposomes with anionic nucleic acids or proteins extended research toward liposome application and opened the way for development of a large spectrum of products. However, liposomology still faces major deficiencies including: lack of control over drug release rate; sufficient loading of drugs for which pH and ion gradients do not apply; lack of means to override biological barriers (i.e. skin, blood–brain barrier); therapeutically efficient active targeting; and for a broad spectrum of non-medical applications, cheaper suitable raw materials (lipids). Overcoming these deficiencies is the current challenge of research and development of liposome application.     

Electronic structure methods for studying surface-enhanced Raman scattering

This critical review highlights recent advances in using electronic structure methods to study surface-enhanced Raman scattering. Examples showing how electronic structure methods, in particular time-dependent density functional theory, can be used to gain microscopic insights into the enhancement mechanism are presented (150 references).     

Raman-based geobarometry of ultrahigh-pressure metamorphic rocks: applications, problems, and perspectives

Raman-based geobarometry has recently become increasingly popular because it is an elegant way to obtain information on peak metamorphic conditions or the entire pressure-temperature-time (P-T-t) path of metamorphic rocks, especially those formed under ultrahigh-pressure (UHP) conditions. However, several problems need to be solved to get reliable estimates of metamorphic conditions. In this paper we present some examples of difficulties which can arise during the Raman spectroscopy study of solid inclusions from ultrahigh-pressure metamorphic rocks.     

Macrocycle-based oligo- and polylactides: synthesis and prospects of application

The review considers methods for modifying oligo- and polymers of lactic acid by macrocyclic moieties (cyclodextrin, tetrapyrrole, and calixarene) and the effect of modifiers on the complexing, thermal, and aggregation properties. Analytical characteristics of oligolactide-based sensors and biosensors are discussed, with particular emphasis on the mechanism of signal generation and the contribution of modified materials to the selectivity and sensitivity of analysis.

     

Nanomaterials in mass spectrometry ionization and prospects for biological application

The rapid development of nanotechnology has revolutionized scientific developments in recent decades. Mass spectrometry (MS) measurements are no exception and have benefited greatly from integration of nanomaterials in every step of analysis. This brief review summarizes recent developments in the field with the focus on the use of nanomaterials as alternative media to facilitate analyte ionization in laser-desorption ionization–mass spectrometry (LDI–MS) and secondary ion mass spectrometry (SIMS). The biological applications of both techniques are also detailed. The use of nanomaterials in other aspects of MS analysis, for example in sample clean-up and indirect analyte quantification, is briefly discussed.     

Sugar-mimic glycosidase inhibitors: natural occurrence,biological activity and prospects for therapeutic application

Alkaloids mimicking the structures of monosaccharides are now believed to be widespread in plants and microorganisms, and these sugar mimics inhibit glycosidases because of a structural resemblance to the sugar moiety of the natural substrate. Naturally occurring sugar mimics with a nitrogen in the ring are classified into five structural classes: polyhydroxylated piperidines, pyrrolidines, indolizidines, pyrrolizidines and nortropanes. Glycosidases are involved in a wide range of important biological processes, such as intestinal digestion, post-translational processing of glycoproteins and the lysosomal catabolism of glycoconjugates. The realization that alkaloidal sugar mimics might have enormous therapeutic potential in many diseases such as viral infection, cancer and diabetes has led to increasing interest and demand for these compounds. Most of these effects can be shown to result from the direct or indirect inhibition of glycosidases. The glycosphingolipid (GSL) storage diseases are relatively rare hereditary disorders that are severe in nature and frequently fatal. Possible strategies for the treatment of these lysosomal storage diseases include enzyme replacement therapy, gene therapy and substrate deprivation. Recently, quite a new therapy for lysosomal storage diseases has been reported, namely a ‘chemical chaperone therapy’ for Fabry disease. In this report, the structural basis for the specificity of inhibition of alkaloidal sugar mimics and their current and potential application to biomedical problems will be reviewed.     

Gold nanoparticles for the development of clinical diagnosis methods

The impact of advances in nanotechnology is particularly relevant in biodiagnostics, where nanoparticle-based assays have been developed for specific detection of bioanalytes of clinical interest. Gold nanoparticles show easily tuned physical properties, including unique optical properties, robustness, and high surface areas, making them ideal candidates for developing biomarker platforms. Modulation of these physicochemical properties can be easily achieved by adequate synthetic strategies and give gold nanoparticles advantages over conventional detection methods currently used in clinical diagnostics. The surface of gold nanoparticles can be tailored by ligand functionalization to selectively bind biomarkers. Thiol-linking of DNA and chemical functionalization of gold nanoparticles for specific protein/antibody binding are the most common approaches. Simple and inexpensive methods based on these bio-nanoprobes were initially applied for detection of specific DNA sequences and are presently being expanded to clinical diagnosis. Figure Colorimetric DNA/RNA detection using salt induced aggregation of AuNP-DNA nanoprobes.     

Raman spectroscopic study of crystallization from solutions containing MgSO4 and Na2SO4: Raman spectra of double salts

Mg(2+), Na(+), and SO(4)(2-) are common ions in natural systems, and they are usually found in water bodies. Precipitation processes have great importance in environmental studies because they may be part of complex natural cycles; natural formation of atmospheric particulate matter is just one case. In this work, Na(2)Mg(SO(4))(2)·5H(2)O (konyaite), Na(6)Mg(SO(4))(4) (vanthoffite), and Na(12)Mg(7)(SO(4))(13)·15H(2)O (loeweite) were synthesized and their Raman spectra reported. By slow vaporization (at 20 °C and relative humidity of 60-70%), crystallization experiments were performed within small droplets (diameter ≤ 1-2 mm) of solutions containing MgSO(4) and Na(2)SO(4), and crystal formations were studied by Raman spectroscopy. Crystallization of Na(2)Mg(SO(4))(2)·4H(2)O (bloedite) was observed, and the formation of salt mixtures was confirmed by Raman spectra. Bloedite, konyaite, and loeweite, as well as Na(2)SO(4) and MgSO(4)·6H(2)O, were the components found to occur in different proportions. No crystallization of Na(6)Mg(SO(4))(4) (vanthoffite) was observed under the crystallization condition used in this study.     

Raman spectral imaging of single cancer cells: probing the impact of sample fixation methods

Raman spectroscopy has proven its potential for the analysis of cell constituents and processes. However, sample preparation methods compatible with clinical practice must be implemented for collection of accurate spectral information. This study aims at assessing, using micro-Raman imaging, the effects of some routinely used fixation methods such as formalin-fixation, formalin-fixation/air drying, cytocentrifugation, and air drying on intracellular spectral information. Data were compared with those acquired from single living cells. In parallel to these spectral information, cell morphological modifications that accompany sample preparation were compared. Spectral images of isolated cells were first analyzed in an unsupervised way using hierarchical cluster analysis (HCA), which allowed delimitation of the cellular compartments. The resulting nuclei cluster centers were compared and revealed at the molecular level that fixation induced changes in spectral information assigned to nucleic acids and proteins. In a second approach, a supervised fitting procedure using model spectra of DNA, RNA, and proteins, chemically extracted from living cells, revealed very small modifications at the level of the localization and quantification of these macromolecules. Finally, HCA and principal components analysis (PCA) performed on individual spectra randomly selected from the nuclear regions showed that formalin-fixation and cytocentrifugation are sample preparation methods that have little impact on the biochemical information as compared to living conditions. Any step involving cell air drying seems to accentuate the spectral deviations from the other preparation methods. It is therefore important in a future context of spectral cytology to take into account these variations.     

Boron-containing small rings: synthesis,properties, and application prospects

The studies published over the last 15 years on the synthesis, physicochemical properties, and application prospects of saturated and unsaturated three- and four-membered boron-containing carbocycles with one boron atom — boriranes, borirenes, boretanes, and 1,2-dihydroboretanes — are summarized and systematized. Original methods for the synthesis of boriran(en)es based on photochemical isomerization of organoboranes, double hydroboration of acetylenes with imidazol-2-ylideneboranes, and [2+1]-cycloaddition of borylenes (:B–R) to unsaturated compounds are considered. A new method for the synthesis of substituted boriranes by Cp₂TiCl₂-catalyzed cycloboration of olefins with boron halides in the presence of metallic Mg is presented. The not numerous data on the synthesis of four-membered boracyclanes (boretanes and 1,2-dihydroboretes) based on thermal isomerization of cyclopropylboranes, [2+2]-cycloaddition of methyleneboranes to nitriles, 1,1-diethoxyethylene, or alkynes, as well as transmetallation of 1,8-dilithium naphthalene and titanacyclobutenes with boron halides, are summarized.

     

Soluble colloidal manganese dioxide: Formation, identification and prospects of application

Soluble colloidal MnO₂ was prepared by the reduction of KMnO₄ by three reducing agents as MnSO₄, Na₂S₂O₃ and HCOOH in neutral aqueous solutions at 25°C. Under suitable conditions, these solutions were dark brown in color and found to remain stable and transparent for several weeks. The obtained colloid was characterized by spectrophotometric and coagulation methods. The spectral behavior of soluble colloidal MnO₂ was studied. The λ_max was 390 nm when MnO₂ was prepared by the reduction of KMnO₄ by MnSO₄. Both the λ_max and the molar extinction coefficient depended on the method of preparation of colloidal MnO₂. The formation of MnO₂ was confirmed by the determination of the oxidation state of Mn-species in MnO₂. The behavior of as-prepared colloidal solution obeys Beer Lambert law, if the concentrations of the colloidal particles are assumed to be equal to [MNO ₄ ^? ]₀. Both spectral analysis and that using Rayleigh’s law confirmed the existence of colloidal MnO₂. The observed coagulating efficiency depends not only on the concentration of electrolyte but also on the charge carried by the cation of the electrolyte. Stability of the colloidal particles in the aqueous solutions is determined by the negative charge on the surface of the colloidal particles.     

High-pressure Raman scattering of MgMoO4

In this paper, we present results of high-pressure Raman scattering studies in β-MgMoO₄ from atmospheric to 8.5 GPa. The experiments were carried out using methanol–ethanol as pressure medium. By analyzing the pressure dependence of the Raman data (change in the number of lattice modes, splitting of bands and wavenumber discontinuities) we were able to observe a phase transition undergone by the β-MgMoO₄ at 1.4 GPa, which is only completed at ∼5 GPa. The transition was observed to be irreversible and the modifications in the Raman spectra were attributed to the changes in coordination of Mo ions from tetrahedral to octahedral. The transition possibly changes the original C2/m symmetry to C2/m or to P2/c. Implication on the phase transition for similar molybdate structures, such as α-MnMoO₄, is also highlighted.     

New spectroscopic method for aqueous solutions: Raman xi-function dispersion for NaClO4 in water

A new Raman method is exemplified by xi identical with-RT[ partial differential ln(I(omega)I(REF)) partial differentialX(1)](T,P,n(2),n(3) ) for ternary NaClO(4)D(2)OH(2)O, or by xi identical with-RT[ partial differential ln(I(omega)I(REF)) partial differentialX(2)](T,P) for binary NaClO(4)H(2)O solutions. (Fundamental differences exist between xi and the chemical potential mu.) I(omega) is the Raman intensity at omega, I(REF) is the reference intensity, e.g., at the isosbestic frequency, X(2) is the H(2)O and X(1) the small D(2)O mol fraction, and n(2) and n(3) are constant mols of H(2)O and NaClO(4), respectively. Maxima (max) and minima (min) were observed in xi versus omega (cm(-1)); xi(max)-xi(min)=Deltaxi(max). Deltaxi(max)=8050+/-100 calmol H(2)O for the coupled, binary solution OH stretch, and Deltaxi(max)=4200+/-200 calmol H bond for the decoupled, ternary solution OD stretch. The perchlorate ion breaks the H bonds in water. 8050 calmol H(2)O corresponds to the maximum tetrahedral Deltaxi(max) value for two H bonds, i.e., Deltaxi(max)=4025 calmol H bond, in agreement with the HDO Deltaxi(max)=4200+/-200 calmol H bond. [Deltaxi(max) is not the H bond enthalpy (energy).] Minima occur in xi at the peak omega values corresponding to the HDOH(2)O and H(2)O ices, and maxima in xi at 2637+/-5 cm(-1) (OD) and 3575+/-10 cm(-1) (OH) correspond to the peak OD and OH stretching omega values from dense supercritical water. Enthalpy dispersion curves were also determined for saturated, binary, and ternary NaClO(4) solutions and for D(2)O in H(2)O. The xi-function method is shown to be applicable to infrared absorbance spectra.     

Measurement of the stability constants for aqueous calcium and magnesium nitrite by Raman spectroscopic methods

Raman and infrared spectroscopic studies have been performed on aqueous calcium and magnesium nitrite solutions over a wide range of solution compositions. Stability constants have been calculated from quantitative intensity measurement of bands in the v₂ nitrite region arising from free and complexed nitrite. The measured values at 25°C. are: Ca(NO₂)₂, ₁ = 0.18 at ionic strength 5.8; Mg(NO₂)₂, ₁ = 0.061 at ionic strength 8.2. The populations of calcium nitrite complexes were found to increase considerably with increased ionic strenth, but complex formation was not temperature-sensitive in either case. Differences in relative intensities, between infrared and Raman spectra are discussed.Based on the thesis of B. S. DeYoung submitted in partial fulfillment of the requirements for an Honours B.Sc. degree, Memorial University of Newfoundland.     

Ionic liquids in enzymatic catalysis and biochemical methods of analysis: Capabilities and prospects

The first Russian review systematizes and discusses the most important and promising published data on the use of ionic liquids in biocatalysis and, especially, biochemical methods of analysis. Studies on the use of ionic liquids as solvents for enzymes, new reaction media for enzymatic reactions, and components of the biosensitive layers of sensors are analyzed. The physical and chemical properties of ionic liquids used in biocatalysis are discussed. The advantages of ionic liquids over the usual solvents in homogeneous and heterogeneous reactions with the participation of enzymes from various classes are demonstrated, procedures for the coimmobilization of biocatalysts and ionic liquids with cellulose onto polymer supports and electrodes are described, and prospects for the use of enzyme-ionic liquid compositions in biochemical methods of analysis are considered.     

The application of thermoanalytical methods for the characterization of zeolite catalysts

Through the coupling of a DSC 111 (Setaram) with a gas dosing valve and a catharometer detector, equipment was developed for the investigation of adsorbents and catalysts. This equipment was applied for the determination of differential and integral heats of adsorption of C₂ to C₄ hydrocarbons on zeolites of the pentasile family. The proposed method has sufficient accuracy for the determination of adsorption heats for technical products. The advantages and the problems of the presented method are discussed.

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Zusammenfassung Durch Kombination eines DSC-Geräts (Setaram Typ 111) mit einem Gasdosierventil und einem Wärmeleitfähigkeitsdetektor wurde ein Gerät für die Untersuchung von Adsorbentien und Katalysatoren geschaffen. Dieses Gerät wurde zur Bestimmung difierentieller und integraler Adsorptionswärmen von C₂- bis C₄-Kohlenwasserstoffen an Zeolithen der Pentasil-Familie eingesetzt. Die vorgeschlagene Methode ist ausreichend genau, um Adsorptionswärmen technischer Produkte zu bestimmen. Vorzüge und Probleme der Methode werden diskutiert.

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111 () - - , . C₂ C₄ . . .