Sergio Bonora

Adsorption and conformational change of myoglobin on biomimetic hydroxyapatite nanocrystals functionalized with alendronate.

The chemical conjugation of bisphosphonates (BPs), specifically alendronate, to hydroxyapatite could be an effective means to impart to it fine-tuned bioactivity. Horse heart myoglobin (Mb), a well-characterized protein, has been adsorbed onto biomimetic hydroxyapatite nanocrystals (nHA) and onto the nHA/alendronate conjugate powdered samples. The obtained materials have potential use in bone implantation and as prospective drug-delivery devices. The kinetic absorption of Mb onto nHA is dramatically affected by its functionalization with alendronate. The covering of the nHA surface by alendronate inhibits the adsorption of myoglobin. The adsorption mechanisms of the protein were studied by spectroscopic techniques (UV-vis and surface-enhanced Raman spectroscopy). The results indicate that the protein changes conformation upon adsorption on the inorganic substrate. In particular, the interaction with nHA alters the coordination state of the iron in the heme through the formation of a hexacoordinated low-spin Mb heme, possibly involving the distal histidine. Instead, the covering of the nHA surface by alendronate does not adsorb the protein but preserves the coordination state of the heme moiety. This study could be of significance either in the field of biomaterials science, in particular, to fine tune a bone-specific drug delivery device and to test nHA as a new support for heterogeneous catalysis, improving the understating of enzyme immobilization.

Raman and IR spectroscopic investigation of zinc(II)-carnosine complexes.

The zinc(II)-L-carnosine system was investigated at different pH and metal/ligand ratios by Raman and IR spectroscopy. The Raman and IR spectra present some marker bands useful to identify the sites involved in metal chelation at a specific pH value. In particular, the neutral imidazole group gives rise to some Raman bands, such as the nu C(4)===C(5) band, that change in wave number, depending on whether the imidazole ring takes the tautomeric form I or II. Even if tautomer I is predominant in the free ligand, metal coordination can upset tautomeric preference and N(tau)- and N(pi)-ligated complexes can be identified. Although weak compared to those of aromatic residues, these Raman marker bands may be useful in analyzing metal-histidine interaction in peptides and proteins. On the basis of the vibrational results, conclusions can be drawn on the species existing in the system. Depending on the available nitrogen atoms, various complexes can be formed and the prevalent form of the species depends mainly on the pH. At basic pH carnosine gives rise to two different neutral complexes: a water-insoluble polymeric species, [ZnH(-1)L](0)(n), and a dimer, [Zn(2)H(-2)L(2)](0). The first is predominant and involves the tautomeric I form of the imidazole ring in metal chelation; the second contains tautomer II and increases its percentage by going from a 2 to 0.25 metal/ligand ratio. Conversely, the dimeric species dominates at pH 7, whereas two charged species, [ZnHL](2+) and [ZnL](+), are formed under slightly acidic conditions. In the [ZnHL](2+) complex the imidazole ring takes part in the Zn(II) coordination in the tautomeric I form, whereas in [ZnL](+) the ring is protonated and not bound to the Zn(II) ion. In addition, the curve fitting analysis of the 1700-1530 cm(-1) Raman region was helpful in indicating the predominant species at each pH.

Raman and FT IR ATR study of diethylsulfoxide/water mixtures

Abstract The Raman and FT IR ATR spectra of diethylsulfoxide (DESO)-water mixtures in the SO and C–H stretching vibration regions at different molar ratios are considered. Noticeable changes are observed in the ν SO region, suggesting the existence of strong H-bonds between DESO and water molecules; on the contrary the ν CH bands change only in a less extent, supporting the existence of SO⋯HC hydrogen bonds in pure DESO that gradually break in the presence of water. In addition, FT IR measurements confirm the existence of ‘free’ SO group at low concentrations of DESO. The results obtained are well explainable in frame of the cluster-structure model of liquid water.

DSC and Raman study on the interaction between polychlorinated biphenyls (PCB) and phospholipid liposomes

Polychlorinated biphenyls (PCB) are very toxic lipophilic substances widely used in the past as non flammable dielectric fluids. PCB accumulation in the environment appears to be a great risk for human health. Dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphatidylethanolamine (DMPE) liposomes with increasing amounts of Aroclor 1254 have been studied by DSC and Raman spectroscopy. Noticeable changes take place in thermograms and Raman spectra even in the presence of small amounts of Aroclor, suggesting the existence of strong interactions due to the insertion of the PCB molecules into the hydrophobic core of liposomes. In DPPC liposomes, a ‘solution like’ system is observed and the main effects are the decrease of both the melting temperature and ΔH of transition, with a simultaneous increase in the half width and asymmetry of the peak. On the contrary, in DMPE liposomes, a complex structure of the thermograms, which comes from the coexistence of different phases, is observed in most of the analysed systems. The behaviour is explained on the basis of a different penetration depth into the bilayer due to the polar interactions involving the polar head of the lipid. The existence of an interdigitate phase in DMPE–PCB liposomes is also evident in the experimental results.

Recent applications of vibrational mid-Infrared (IR) spectroscopy for studying soil components: a review

The present review highlights the recent applications of mid-infrared spectroscopy and in particular of diffuse reflectance spectroscopy (DRIFT) and attenuated total reflectance (ATR) and processing methods (e.g., deconvolution, derivative and chemometrics) to rapidly provide valuable information on soil composition and organic geochemistry. Research has demonstrated that both DRIFT and ATR techniques can be considered useful tools for the analysis of a large number of soil samples, giving not only typical spectral patterns but permitting an accurate prediction of quantitative parameters such as, e.g., total carbon, total nitrogen, C/N ratio, lignin, dissolved OC, carbonyl-C, aromatic-C, O-alkyl-C, and alkyl-C contents. Based on literature results, infrared spectroscopy can be recognized as one of the most promising analytical techniques for investigating soil science.

Vibrational spectra of diethylsulfoxide

FT IR and Raman spectroscopic studies of pure diethylsulfoxide (DESO) in the liquid and in the solid states and its solutions in various solvents have been performed. Analysis of SO- and CH-stretching regions in a wide range of concentration shows that the bands may be fitted satisfactorily by considering seven components. In addition, fundamental frequencies have been assigned using ab initio calculations at the RHF/3-21G* levels. The results obtained confirm a viewpoint on a self-associative structure of DESO, and support the hypothesis of the existence of different types of intermolecular associates including both dipole-dipole and hydrogen bonding mechanisms.

Influence of sebacate plasticizers on the thermal behaviour of dipalmitoylphosphatidylcholine liposomes

Sebacic acid esters are a promising class of low toxicity plasticizers for PVC. They are lipophylic substances and thus, their interaction with biomembranes must be considered. DPPC liposomes in the presence of increasing amounts of dimethylsebacate (DMS), diethylsebacate (DES), dibutylsebacate (DBS) and di-(2-ethylhexyl)sebacate (DEHS) have been studied by DSC, both on heating and cooling. As a general feature, the melting point decreases and the enthalpy ΔH increases along with the half-width and asymmetry of the transition in most of the systems. The observed effects are strongly dependent on the length and the shape of the ester-chains suggesting that both polar interactions between carboxylic groups of sebacates and the polar heads of the lipids as well the hydrophobic interactions involving penetration into the bilayer are important. The effects are noticeable also in the presence of small amounts of plasticizers. In the presence of large amounts of DES and DBS, a complex structure of the transition arising from the coexistence of aggregates of different types and also the appearance of new phases were observed. The behaviour of sebacates to model biomembranes is quite different for other classes of lipophylic PVC plasticizers, such as phthalates and we explain the differences on the basis of the greater flexibility of the sebacic acid chain.

Hydrogen bonds in calcium acid phosphates by infrared and Raman spectra

Abstract Infrared and Raman spectra of Ca(H2PO4)2, Ca(H2PO4)2·H2O and deuterated analogues are presented and discussed. The behaviour of the asymmetric stretching vibration νOH and of the in-plane δOH and out-of-plane γOH deformations shows that hydrogen bonds of different strengths are present in both compounds, in agreement with X-ray diffraction data. The perturbation brought about by the water molecule on the strength of the hydrogen bond is also considered.

EPA or DHA Supplementation Increases Triacylglycerol, but not Phospholipid, Levels in Isolated Rat Cardiomyocytes

It is well recognized that a high dietary intake of long-chain polyunsaturated fatty acids (LC-PUFA) has profound benefits on health and prevention of chronic diseases. In particular, in recent years there has been a dramatic surge of interest in the health effects of n-3 LC-PUFA derived from fish, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. Notwithstanding, the metabolic fate and the effects of these fatty acids once inside the cell has seldom been comprehensively investigated. Using cultured neonatal rat cardiomyocytes as model system we have investigated for the first time, by means of high-resolution magic-angle spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy in combination with gas chromatography (GC), the modification occurring in the cell lipid environment after EPA and DHA supplementation. The most important difference between control and n-3 LC-PUFA-supplemented cardiomyocytes highlighted by HR-MAS NMR spectroscopy is the increase of signals from mobile lipids, identified as triacylglycerols (TAG). The observed increase of mobile TAG is a metabolic response to n-3 LC-PUFA supplementation, which leads to an increased lipid storage. The sequestration of mobile lipids in lipid bodies provides a deposit of stored energy that can be accessed in a regulated fashion according to metabolic need. Interestingly, while n-3 LC-PUFA supplementation to neonatal rat cardiomyocytes causes a huge variation in the cell lipid environment, it does not induce detectable modifications in water-soluble metabolites, suggesting negligible interference with normal metabolic processes.

DSC Study on the Interaction Between Bis-2-(Ethylhexyl) Phthalate and Other o-phthalic Acid Esters and Dipalmitoyl Phosphatidylcholine Liposomes

Phthalic acid esters, and in particular bis-2-(ethylhexyl) phthalate, are common environmental contaminants with long-term toxic and carcinogenic effects that readily dissolve in lipid substances. DSC measurements of hydrated multilamellar dipalmitoyl phosphatidylcholine liposomes in the presence of different amounts of bis-2-(ethylhexyl) phthalate, dioctyl phthalate, dibutyl phthalate (DBP) and diethyl phthalate (DEP) were considered. The effects on the main transition temperature, ΔH, and the shape and width of the transition were studied.A decrease in Tm, without an accompanying decrease in ΔH,and increases in both the asymmetry and the width of the main transition peak were observed.In some cases, the calorimetric curve showed complex peak structures arising from the coexistence of various aggregates of different sizes. This was particularly evident in the liposomes with DEP and DBP contents ranging from 5.0 to 7.5% m/m.For all the considered model systems, the effects were noticeable even in the presence of small amounts of phthalates; in the presence of greater amounts, the overall structure of the bilayer was in some cases strongly modified, with the appearance of new different phases.Since the function of a membrane-associated protein is dependent on the lipid structure, phthalates could modify the function by modifying the membrane structure.