FTIR spectroscopy in medical mycology: applications to the differentiation and typing of <Emphasis Type="Italic">Candida</Emphasis>

The incidence of fungal infections, in particular candidiasis and aspergillosis, has considerably increased during the last three decades. This is mainly due to advances in medical treatments and technologies. In high risk patients (e.g. in haematology or intensive care), the prognosis of invasive candidiasis is relatively poor. Therefore, a rapid and correct identification of the infectious agent is important for an efficient and prompt therapy. Most clinical laboratories rely on conventional identification methods that are based on morphological, physiological and nutritional characteristics. However, these have their limitations because they are time-consuming and not always very accurate. Moreover, molecular methods may be required to determine the genetic relationship between the infectious strains, for instance in Candida outbreaks. In addition, the latter methods require time, expensive consumables and highly trained staff to be performed adequately. In this study, we have applied the FTIR spectroscopic approach to different situations encountered in routine mycological diagnosis. We show the potentials of this phenotypic approach, used in parallel with routine identification methods, for the differentiation of 3 frequently encountered Candida species (C. albicans, C. glabrata and C. krusei) by using both suspensions and microcolonies. This approach, developed for an early discrimination, may help in the initial choice of antifungal treatment. Furthermore, we demonstrate the feasibility of the method for intraspecies comparison (typing) of 3 Candida species (C. albicans, C. glabrata and C. parapsilosis), particularly when an outbreak is suspected.     

Use of a single calibration graph for the determination of major elements in geological materials by laser ablation inductively coupled plasma atomic emission spectrometry with added internal standards

The possibility of internal standardisation in laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES) of geological materials by added Sc₂O₃ and Y₂O₃ has been examined to cover the wide range of concentrations of major and minor constituents both in silicate rocks and limestones. A Nd : YAG laser (355 nm, 10 Hz, 10 mJ per shot) was used for the ablation of discs obtained by fusion of the mixture of samples and oxides of Sc and Y with lithium tetraborate. The flux/sample ratio was in the range from 6 to 10. The contents of analytes were within the concentration range from hundredths to tens of percentage. The trace elements copper and nickel were studied, too. An ICP emission spectrometer OPTIMA 3000 DV was used for the measurement of Si, Al, Ca, Mg, Sr, Ba, Fe, Ti, Mn, Ni, Cu, Na and K analyte lines and Y and Sc reference lines in the axial observation mode. The long-term and the short-term repeatability of measurement were improved by employing scandium or yttrium internal references lines for the above analytes from 6% to 1.5% of RSD and from 2.4% to 1.0% of RSD, respectively. The correlation of signals with concentrations was improved in terms of the correlation coefficient r from 0.90–0.97 to 0.98–0.998 and the relative uncertainity on the centroid of concentrations was improved 2–3 times. A single calibration graph covering the concentration range both in silicates and carbonates is possible for each of elements, as the matrix effects are compensated for by internal standards and the excess of Li₂B₄O₇. Received: 20 June 1998 / Revised: 20 July 1998 / Accepted: 21 September 1998     

Photobleaching of Arterial Fluorescent Compounds: Characterization of Elastin, Collagen and Cholesterol Time-resolved Spectra during Prolonged Ultraviolet Irradiation

To study the photobleaching of the main fluorescent compounds of the arterial wall, we repeatedly measured the time-resolved fluorescence of elastin, collagen and cholesterol during 560 s of excitation with nitrogen laser pulses. Three fluence rate levels were used: 0.72, 7.25 and 21.75 microW/mm2. The irradiation-related changes of the fluorescence intensity and of the time-resolved fluorescence decay constants were characterized for the emission at 390, 430 and 470 nm. The fluorescence intensity at 390 nm decreased by 25-35% when the fluence delivered was 4 mJ/mm2, a common value in fluorescence studies of the arterial wall. Cholesterol fluorescence photobleached the most, and elastin fluorescence photobleached the least. Photobleaching was most intense at 390 nm and least intense at 470 nm such that the emission spectra of the three compounds were markedly distorted by photobleaching. The time-resolved decay constants and the fluorescence lifetime were not altered by irradiation when the fluence was below 4 mJ/mm2. The spectral distortions associated with photobleaching complicate the interpretation of arterial wall fluorescence in terms of tissue content in elastin, collagen and cholesterol. Use of the time-dependent features of the emission that are not altered by photobleaching should increase the accuracy of arterial wall analysis by fluorescence spectroscopy.     

Solubility and Raman Spectroscopic Study of As(III) Speciation in Organic Compound-Water Solutions. A Hydration Approach for Aqueous Arsenic in Complex Solutions

Solubilities of arsenolite (As₂O₃, cub.) were measured from 22 to 90°C in water–acetone, water–acetic acid, and water—formic acid solutions of compositions ranging from the pure organic compound to pure water. Raman spectra were obtained at ambient temperature on As-containing water–acetic acid and water–acetone solutions. Results show that arsenic solvation by these organic compounds is negligible and hydroxide species dominate As speciation over a wide range of water activity (a_{H 2 O}> 0.01). The solubility data were analyzed using an approach based on stoichiometric hydration reactions. Results show that As₂O₃ solubility can be described as a function of water activity, independently of the nature of the organic compound, by involving two neutral As hydroxide complexes: As(OH)₃ and As(OH)₃·4H₂O. Stability constants derived for these species indicate that hydration weakens with increasing temperature. Calculations using these constants show that at low temperatures the tetrahydrate As(OH)₃·4H₂O is dominant in water-rich solutions; by contrast, in high-temperature crustal fluids, As(OH)₃ becomes the major As species. The proposed hydration model can be used to analyze solubility of arsenic-bearing minerals and arsenic transport in complex H₂O–CO₂—electrolyte solutions encountered in natural and industrial environments.     

Decreased Electron Transfer Rates of Manganese Porphyrins with Conformational Distortion of the Macrocycle

Slow electron transfer to manganese(iii) porphyrins results when the macrocycle deviates from planarity. This was demonstrated by measuring the kinetics of homogeneous electron transfer from a series of semiquinone radical anions to synthetic manganese porphyrins (shown schematically; R¹=H, Cl, F; R²=H, F). Three of the four porphyrins studied have nonplanar macrocycles. These results could have implications for the role of manganese in biological electron transfer processes.     

A Convergent Strategy for the Asymmetric Synthesis of Enantiomerically Pure Bicyclic Compounds by Using a Silicon-Directed Cycloaddition Reaction: The Synthesis of Enantiomerically Pure Bicyclo[3.2.0]hept-2-en-6-one

An asymmetric allylmetalation followed by a silicon-stereodirected cycloaddition gives enantiomerically pure bicyclic compounds. The synthesis of enantiopure 1 (see scheme) in a yield of 65–74 %, 93 % ee, and >98 % de provides an illustration of the efficacy of the method. The preferential formation of 1 rather than its diastereoisomer (32:1), during the cycloaddition step, matches the result predicted by RHF and density functional theory studies.     

Influence of nanometer scale film structure of ZDDP tribofilm on Its mechanical properties: A computational chemistry study

We investigated the influence of a nanometer scale film structure of a tribofilm generated from zinc dialkyldithiophosphate (ZDDP) anti-wear additive on its mechanical properties using a combined molecular dynamics (MD) and finite element (FE) method. The frictional behavior of an interface between a native iron oxide layer on steel surface and zinc metaphosphate - regarded as a model material of ZDDP tribofilm - was firstly studied using the MD method. The results showed that the iron atoms in the oxide layer diffused into the phosphate layer during the friction process. The zinc atoms in the phosphate layer also diffused into the oxide layer. Significant interdiffusion of iron and zinc atoms was observed with increasing simulation time. Thus, metallic phosphate with a gradient composition of iron and zinc atoms was formed on the phosphate/oxide interface. We then constructed an axisymmetric nanoindentation simulation model from the MD-derived structures at a certain simulation time and carried out a FE calculation. As a result, we found that the rubbed ZDDP tribofilm, including the phosphate with the gradient composition of metallic atoms, showed larger contact stiffness and hardness. The combined MD/FE simulation indicates that the tribofilm becomes stiffer and harder due to the interdiffusion of iron and zinc atoms on the tribofilm/oxide interface. We have found that the gradient composition formation in ZDDP tribofilm during friction process influences on its mechanical properties.     

Hydrothermal synthesis of large maghemite nanoparticles: influence of the pH on the particle size

Maghemite nanoparticles with sizes in the range 10–110 nm and good monodispersity have been synthesized by co precipitation at room temperature from Fe²⁺ and Fe³⁺ ions by a (N(CH₃)₄OH) solution, followed by an hydrothermal treatment at 200 °C and an oxidation step with Fe(NO₃)₃. The influence of the incubation time (at 200 °C) and of the pH of the autoclaved solution on the particles size has been studied. It was found that the pH value allows to tune the size of the maghemite particles. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Intravascular ultrasound allows a hyperplasia diagnosis in vivo in rat as accurate as histomorphometry

Objective and motivation

Intravascular ultrasound (IVUS) allows in vivo invasive intra-luminal real-time examination of the arterial wall structure. In this study, we aimed to validate for the first time the in vivo IVUS performing as a diagnostic tool by comparison to the well-established histomorphometry approach, in the largely used rat model of carotid angioplasty model that mimics the angioplasty procedure in humans.

Methods

Atherosclerotic lesions were allowed to develop during four weeks after balloon catheter inflation of the left carotid artery, whereas the intact right carotid artery was used as control. Four weeks after injury, a Boston Scientific 40 MHz device to perform IVUS exams in vivo on both carotid arteries. Then, both carotid arteries were examined in vitro by histomorphometry and correlation between IVUS and histomorphometric parameters (plaque plus media cross-sectional areas [CSA] and eccentricity index) were researched.

Results

After ANOVA analysis, comparative statistical analysis showed significant correlations between IVUS and histomorphometry when examining the intact right carotid artery (r = 0.662 with p < 0.003 for plaque plus media CSA; r = 0.774 with p < 0.002 for eccentricity index), but also when exploring the injured left carotid artery (r = 0.805 with p < 0.0001 for plaque plus media CSA; r = 0.775 with p < 0.002 for eccentricity index).

Conclusions and outcome

We report here for the first time the ability of IVUS to study therapeutic vascular effects in vivo in alive rats. This result is of major importance since it will allow this device to be used for restenosis drug testing in rat model of carotid angioplasty.     

The dimeric unit [La(H2O)4(m-PO3C6H4COOH)(m-PO2(OH)C6H4COOH)(m-PO(OH)2C6H4COOH)]2 as building block of layered hybrid material

A new hybrid organic–inorganic material with the structural formula unit [La(H₂O)₄(m-PO₃C₆H₄COOH)(m-PO₂(OH)C₆H₄COOH)(m-PO(OH)₂C₆H₄COOH)]₂ (or [La(H₂O)₄C₂₁H₁₈O₁₅P₃]₂) has been synthesized under hydrothermal condition from La(NO₃)₃·6H₂O and 3-phosphonobenzoic acid (m-PO(OH)₂–C₆H₄–COOH) which is a rigid organic precursor possessing two types of functional groups: phosphonic acid and carboxylic acid. The two units of the produced hybrid are linked together by hydrogen bonds leading to a layered framework composing of by a repetition of inorganic and organic slices. The organic layers consist of dimeric units made of two meta-phosphono-benzoic acid linked together by hydrogen bonds involving their COOH groups. Two kinds of dimeric units are observed: PO₃C₆H₄COOH?HOOCC₆H₄PO(OH)₂, present 2 times in the structure, and PO₂(OH)C6H4COOH?HOOCC₆H₄PO₂(OH). The material crystallises in a monoclinic cell (C2/c (15) space group) with the following parameters: a = 42.515(4) Å, b = 7.4378(6) Å, c = 20.307(2) Å, β = 118.031(6)°, V = 5668.2(9) Å³, Z = 4, density = 1.908 g/cm³.