Quantification of polymeric mannose in wine extracts by FT-IR spectroscopy and OSC-PLS1 regression

FT-IR spectroscopy has being a widespread technique in the agro-industry for the quick assess of food components, including the wine. Using the region of wavenumbers 1200–800 cm⁻¹ of the FT-IR spectra wine polysaccharides, Partial Least Squares Regression (PLS1) independent calibration models were built for mannose quantification in complex matrices from white and in red wine extracts. With PLS1 it was not possible to build a calibration model that included both white and red wine extracts. However, a predictive ability of the model for quantification of mannose from mannoproteins based on this FT-IR spectral region was achieved by the application of orthogonal signal correction (OSC)-PLS1.     

Molecular structure and dielectric properties studies of chitin and its treated by acid, base and hypochlorite

In this work, the chitin was treated by 0.1 N HCl, 0.5 N NaOH, and 8% sodium hypochlorite. The change of the molecular structure was studied by Fourier Transform Infrared Spectroscopy (FTIR) in the wavenumber range (400–4000 cm⁻¹). The absorption bands were assigned and the crystallinity index was calculated from the ratio of the absorbance C–N band at 1378 cm⁻¹ and CH at 2925 cm⁻¹. The data indicated that, the crystallinity index of chitin is higher than that of treated chitin which is due to the hydrolysis of some acetamide group. Also, treating with alkali causes a swelling of chitin chains. The dielectric properties such as dielectric constant (ε′), dielectric loss (ε″) and AC electrical conductivity were measured and discussed as a function of frequencies (0.1 kHz–3 MHz). The dielectric constant (ε′) was decreased with increasing frequencies due to the dielectric dispersion. β-relaxation was observed and discussed from the dielectric loss (ε″). The results of AC conductivity showed that, at high frequency, the conductivity increased with increasing frequencies and its interpreted in term of hopping conduction.     

Characterization of cotton fabric scouring by FT-IR ATR spectroscopy

FT-IR attenuated total reflectance (ATR) spectroscopy has been used for the fast characterization of cotton fabric scouring process. The greige and the scoured cotton fabrics showed very similar FT-IR spectrum in transmission mode because the bulk composition of the fabrics are similar. However, FT-IR ATR spectroscopy can provide information about the surface of a fabric. By examination of C–H stretching region at 2800–3000 cm⁻¹, the amount of waxes left on the fabric can be estimated. The presence of pectins and/or waxes can also be probed by observation of carbonyl peak induced by the HCl vapor treatment on the fabric. Based on these changes of FT-IR ATR spectra, the scouring process has been characterized.     

Fourier-transform infrared spectroscopic study of globulin from Phaseolus angularis (red bean).

The conformation of red bean globulin dispersions (≈10% in D₂O or deuterated phosphate buffer pD 7.4) under the influence of pH, chaotropic salts, protein structure perturbants, and heating conditions was studied by Fourier-transform infrared (FTIR) spectroscopy. The FTIR spectrum of red bean globulin showed major bands from 1682 to 1637 cm⁻¹ in the amide I′ region, corresponding to the four types of secondary structures, i.e. β-turns, β-sheets, -helix and random coils. At extreme pH conditions, there were changes in intensity in bands attributed to β-sheet (1637 and 1618 cm⁻¹) and random coil (1644 cm⁻¹) structures, and shifts of these bands to lower or higher wavenumbers, indicating changes in protein conformation. Chaotropic salts caused progressive increases in random coil structures and concomitant decreases in β-sheet bands, following the lyotrophic series of anions. In the presence of sodium dodecyl sulfate and ethylene glycol, pronounced increases in the random coil band were observed, accompanied by slight shifts of the β-sheet band. Addition of dithiothreitol and N-ethylmaleimide did not cause marked changes in the FTIR spectra. Heating at increasing temperature led to progressive decreases in the intensity of the -helix and β-sheet bands and increases in random coil band intensity, leveling off at around 60 °C. The data suggest that re-organization of protein structure occurred at temperatures well below the denaturation temperature of red bean globulin (86 °C) as determined by differential scanning calorimetry. This was accompanied by pronounced increases in the intensity of the two intermolecular β-sheet bands (1682 and 1619–1620 cm⁻¹) associated with the formation of aggregated strands at higher temperatures (80–90 °C). Increases in intensity of the aggregation bands were also observed in the heat-induced buffer-soluble and insoluble aggregates.     

Fourier transform infrared spectroscopy used to evidence the prevention of beta-sheet formation of amyloid beta(1-40) peptide by a short amyloid fragment

Reflectance Fourier transform infrared (FT-IR) microspectroscopy was applied to study the prevention of β-sheet formation of amyloid β (Aβ)(1–40) peptide by co-incubation with a hexapeptide containing a KLVFF sequence (Aβ(15–20) fragment). Second-derivative spectral analysis was used to locate the position of the overlapping components of the amide I band of Aβ peptide and assigned them to different secondary components. The result indicates that each intact sample of Aβ(15–20) fragment or Aβ(1–40) peptide previously incubated in distilled water at 37 °C transformed their secondary structure from 1649 (1651) or 1653 cm⁻¹ to 1624 cm⁻¹, suggesting the transformation from -helix and/or random coil structures to β-sheet structure. By co-incubating both samples with different molar ratio in distilled water at 37 °C, the structural transformation was not found for Aβ(1–40) peptide after 24 h-incubation. But the β-sheet formation of Aβ(1–40) peptide after 48 h-incubation was evidenced from the appearance of the IR peak at 1626 cm⁻¹ by adding a little amount of Aβ(15–20) fragment. There was no β-sheet formation of Aβ(1–40) peptide after addition with much amount of Aβ(15–20) fragment, however, suggesting the higher amount of Aβ(15–20) fragment used might inhibit the β-sheet formation of Aβ(1–40) peptide. The more Aβ(15–20) fragment used made the more stable structure of Aβ(1–40) peptide and the less β-sheet formation of Aβ(1–40) peptide. The study indicates that the reflectance FT-IR microspectroscopy can easily evidence the prevention of β-sheet formation of Aβ(1–40) peptide by a short amyloid fragment.     

FT-IR spectroscopic determination of the degree of esterification of cell wall pectins from stored peaches and correlation to textural changes

The FT-IR spectroscopic study of peach cell walls revealed the existence of two peaks absorbing at 1749 and 1630 cm⁻¹ assigned, respectively, to the absorption of the esterified and non-esterified carboxyl groups of the pectin molecules. A linear relationship between the degree of esterification [(number of esterified carboxylic groups/number of total carboxylic groups)×100] and the ratio of the area underneath the peak at 1749 cm⁻¹ over the sum of the areas underneath the two peaks, at 1749 and 1630 cm⁻¹, was established using the FT-IR spectra of standard compounds. The use of the 2nd derivative and curve-fitting techniques allowed the elimination of spectral interferences from other cell wall components. The degree of esterification (D.E.) of pectins from Redhaven peaches immediately after harvest and during storage was evaluated from FT-IR data. During storage at 0°C, the D.E. remained practically constant up to 35 days. During storage at higher temperatures it decreased approaching a final value — the same for all temperatures. This value was reached after 22 days of storage at 5°C, 15 days at 15°C and after only 6 days at 20°C. The changes in the degree of esterification during storage correlated well to fruit firmness.     

Lipolytic activity in submerged cultures of Issatchenkia orientalis

The ability of the yeast Issatchenkia orientalis CECT 10688 to secrete lipolytic activity in submerged culture was investigated. The yeast was grown in a complex medium supplemented with a fixed concentration of several lipidic compounds (triglycerides, fatty acids). Maximum enzyme activity around 70–80 U cm⁻³ was produced in cultures supplemented with tributyrin. An optimum tributyrin concentration of 10 g dm⁻³ was selected. Several surfactants were added to the cultures, but no significant increase in activity was detected. Finally, the effect of the type of carbon source on lipolytic enzyme production was studied. The best results were obtained with glucose and fructose (60–80 U cm⁻³), while rather low enzyme activity was found in cultures grown on lactose and maltose (about 20 U cm⁻³).     

Conceptual model of seagrass die-off in Florida Bay: Links to biogeochemical processes

Seagrasses are recognized as important plant communities in coastal estuaries and lagoons across both tropical and temperate climes; thus, large-scale seagrass die-off events worldwide are of general concern. In Florida Bay, at the southern terminus of the Florida peninsula, seagrass die-off events up to 4000 ha have been reported and smaller scale mortality events are noted annually. In the present study, we examined several hypothesized causative factors (high temperature, hypersalinity, sulfide toxicity) of seagrass (Thalassia testudinum) mortality in Florida Bay. To test sulfide effects, in situ sulfide production was stimulated by applying a labile carbon source (glucose) to sulfate reducers in the sediment at five sites across the bay (northeastern, northcentral, and southwestern basins). During the one year study, high temperature (32–36 °C) and salinity (> 50 psu) were recorded in the bay associated with a regional drought. We also experienced major seagrass die-off events at two of our southwestern bay sites. These field conditions provided an excellent opportunity to closely examine cause–effect relationships among stressors and die-off events in the field, and verify results of our previous mesocosm experiments. Even though glucose amendments stimulated porewater sulfides in bay sediments (4–8 mmol L^− 1), no significant differences in biomass, short shoot density or final growth rates were found between control and glucose plots. In addition, the highest growth rates and shoot densities were concomitant with maximum water column salinity (> 50 psu) and temperature (32–36 °C), when porewater sulfides were also in the millimolar range. Large-scale seagrass mortality events, encompassing  50% of the entire meadow at one site, occurred at southwestern bay sites when plants were down regulating (slower growth and shoot density), probably in response to shorter day length and lower temperature (30–34 to 23–26 °C) from October, 2004 to January, 2005. Sulfate reduction rates (SRR) were also 2-fold higher in the southwestern (214–488 nmol cm^− 3 d^− 1) versus northcentral and northeastern (97–240 nmol cm^− 3 d^− 1) bay sites, possibly limited by labile carbon, which we found to stimulate SRR 3-fold in northeastern and northcentral bay sites (461–708 nmol cm^− 3 d^− 1) and 4-fold at southwestern bay sites (1211–2036 nmol cm^− 3 d^− 1). Based on a synthesis of the field data reported herein, our mesocosm experiments to date, and contributions by others, we present a conceptual model of seagrass die-off in Florida Bay outlining a cascade of stressors, stimulated by P enrichment, which leads to high O₂ consumption in the system triggering a seagrass die-off event.     

Energy transfer within the isolated light-harvesting B800–850 pigment-protein complex of Rhodobacter sphaeroides

We have used picosecond absorption spectroscopy with low intensity (5 · 10¹¹–5 · 10¹² photons · pulse⁻¹ · cm⁻²) continuously tunable infrared (800–900 nm) pulses to study the energy transfer dynamics in the isolated B800–850 pigment-protein complex of Rhodobacter sphaeroides. Our results suggest the following picture of the energy transfer dynamics: (i) a fast transfer, within approx. 1 ps, from BChl 800 to BChl 850; (ii) transfer among different BChl 800's with a rate which is at the most of the same order of magnitude as that of BChl 800 → BChl 850 transfer; (iii) very fast transfer (k > 1 · 10¹² s⁻¹) between BChl 850 molecules. Assuming Förster type of energy transfer maximum distances of about 22 and 15 Å are obtained for the BChl 800–BChl 850 and BChl 850–BChl 850 separations, respectively.     

Two new hydrothermally synthesised hexamine bridged L–M–L type coordination polymers: Characterisation and magneto-structural correlation

Two new L–M–L type transition metal coordination polymers [M(C₆H₁₂N₄)(NCO)₂(H₂O)₂]_n, where M = Co(II) (1) and Ni(II) (2), have been synthesised under controlled hydrothermal condition and characterised spectroscopically and by thermal analyses. Here hmt or hexamethylenetetramine has behaved as a neutral organic bidentate spacer molecule. Both the complexes crystallise in the monoclinic system as confirmed from single crystal X-ray diffraction studies. Cryomagnetic susceptibility measurements over a wide range of temperature (2–300 K) under 0.5 T magnetic fields show a weak antiferromagnetic interaction of J = −0.65 cm⁻¹ for 1 and −1.6 cm⁻¹ for 2. The values have been given a favorable support by weak covalent and H-bonding interactions between octahedral M(II) metal centers as revealed from X-ray structure determination. The high dimensionality of the structures is probably a manifestation of extensively weak covalent interactions and H-bondings.     

The use of different eye regions in the mantis shrimp Hemisquilla californiensis Stephenson, 1967 (Crustacea: Stomatopoda) for detecting objects

A behavioral assay was used to assess the ability of the stomatopod Hemisquilla californiensis to perceive and respond to a moving target under different wavelengths and intensities of light illumination. Subjects responded to targets rotating horizontally across their visual field by a brief startle response of their eyes or antennules but did not track the targets. Under white light responses were elicited down to a light intensity of 0.9 μW cm^− 2. Responses were seen in blue light at intensities as low as 0.5 μW cm^− 2, and in green light down to 1.0 μW cm^− 2. The animals were less sensitive to red light, with no responses seen at intensities below 3.0 μW cm^− 2. Subjects did not respond to the targets at all under infrared light. This response pattern mirrors the computed sensitivity spectrum of ommatidia in the species' peripheral hemispheres but not that in most of the central bands. We conclude that this species uses the monochromatic vision in the peripheral hemispheres of its eyes to recognize objects and that the sharply tuned color receptors of the central band serve to add supplemental information if light conditions allow.     

Human fibroblast culture on a crosslinked dermal porcine collagen matrix

The use of a novel porcine-derived collagen biomaterial as a dermal tissue engineering matrix was examined. The matrix is derived from porcine dermis, and is processed to retain the native collagen (Type 1) and elastin structure. Human primary fibroblasts were cultured on the matrix to examine its potential for creating a dermal replacement. Attachment of fibroblasts on the collagen was compared to tissue culture plastic and PET membranes. Cell proliferation was assessed using the MTT assay and DAPI staining. For seeding densities of 5×10⁴ and 1×10⁵ cells cm⁻², PET and plastic demonstrated >95% attachment of seeded numbers after 3 h. The collagen matrix reached levels >80% after 3–4 h with no influence of the seeding density. Matrix samples with perforating pores of 40 μm diameter were also studied. After 216 h culture in static culture, with media replacement every 3 days, the final cell numbers reached 2.1×10⁵ (perforated) and 2.0×10⁵ cells cm⁻² (unperforated). In comparison fibroblast culture in a perfusion bioreactor, with continuous media replacement, reached 2.3×10⁵ (unperforated) and 2.5×10⁵ cells cm⁻² (perforated) after 216 h.     

Highly sensitive lactate biosensor by engineering chitosan/PVI-Os/CNT/LOD network nanocomposite

A novel chitosan/PVI-Os(polyvinylimidazole-Os)/CNT(carbon nanotube)/LOD (lactate oxidase) network nanocomposite was constructed on gold electrode for detection of lactate. The composite was nanoengineered by selected matched material components and optimized composition ratio to produce a superior lactate sensor. Positively charged chitosan and PVI-Os were used as the matrix and the mediator to immobilize the negatively charged LOD and to enhance the electron transfer, respectively. CNTs were introduced as the essential component in the composite for the network nanostructure. FESEM (field emission scan electron microscopy) and electrochemical characterization demonstrated that CNT behaved as a cross-linker to network PVI and chitosan due to its nanoscaled and negative charged nature. This significantly improved the conductivity, stability and electroactivity for detection of lactate. The standard deviation of the sensor without CNT in the composite was greatly reduced from 19.6 to 4.9% by addition of CNTs. With optimized conditions the sensitivity and detection limit of the lactate sensor was 19.7 μA mM⁻¹ cm⁻² and 5 μM, respectively. The sensitivity was remarkably improved in comparison to the newly reported values of 0.15–3.85 μA mM⁻¹ cm⁻². This novel nanoengineering approach for selecting matched components to form a network nanostructure could be extended to other enzyme biosensors, and to have broad potential applications in diagnostics, life science and food analysis.     

The infrared absorption of amino acid side chains

Amino acid side chains play fundamental roles in stabilising protein structures and in catalysing enzymatic reactions. These fields are increasingly investigated by infrared spectroscopy at the molecular level. To help the interpretation of the spectra, a review of the infrared absorption of amino acid side chains in H₂O and ²H₂O is given. The spectral region of 2600–900 cm⁻¹ is covered.     

Manganese(II) complexes of an acyclic phenol-based dinucleating ligand with four methoxyethyl chelating arms: synthesis, structure, magnetism and electrochemistry

Dinuclear manganese(II) complexes [Mn₂(bomp)(PhCO₂)₂]BPh₄ (1), [Mn₂(bomp)(MeCO₂)₂]BPh₄ (2), and [Mn₂(bomp)(PhCO₂)₂]PF₆ (3) were synthesized with a dinucleating ligand 2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-methylphenol [H(bomp)]. Dinuclear zinc complex [Zn₂(bomp)(PhCO₂)₂]PF₆ (4) was also synthesized for the purpose of comparison. X-ray analysis revealed that the complex 1·CHCl₃ contains two manganese ions bridged by the phenolic oxygen and two benzoate groups, forming a μ-phenoxo-bis(μ-benzoato)dimanganese(II) core. Magnetic susceptibility measurements of 1–3 over the temperature range 1.8–300 K indicated antiferromagnetic interaction (J=−4 to −6 cm⁻¹). Cyclic voltammograms of 3 showed a quasi-reversible oxidation process at +0.9 V versus a saturated sodium chloride calomel reference electrode, assigned to Mn^IIMn^II/Mn^IIMn^III.     

Purification and characterization of hydrosoluble components from the sap of Chinese lacquer tree Rhus vernicifera

Continuous gradient elution chromatography (CGEC) was employed to purify and separate enzymes and polysaccharides from the sap of Rhus vernicifera Chinese lacquer tree. There are three different molecules with laccase enzyme activity. Two are enzymes of each other (L1, and L2), whereas the third (RL) is an entirely separate entity. Two polysaccharides (GP1 and GP2) were also found. The Rhus laccase (RL), and isoenzymes L1 and L2, have peak molecular masses of 109,100, 120,000, 103,000 respectively; each has four copper atoms per molecule, and the pI values were 8.2, 8.6, and 9.1, respectively. The structure of the laccases was studied by Fourier-transform infrared (FT-IR) and Matrix-assisted laser desorption/ionization time-of flight (MALDI-TOF) mass spectrometry. The typical amide I (1646 cm⁻¹) and amide II (1545 cm⁻¹) bands were observed. The results from MALDI-TOF were similar to those from CGEC, but the molecular mass from the MALDI-TOF was significantly different from that obtained from sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).     

Influence of the alkyl-substituted silane precursor on sol–gel encapsulated lipase activity

Lipase from Candida rugosa was encapsulated within a chemically inert sol–gel support prepared by polycondensation of three precursor types (tetraethoxysilane (TEOS), methyltrimethoxysilane (MTMS) and polydimethylsilane (PDMS)) in the presence and absence of polyethylene glycol (PEG) and polyvinyl alcohol (PVA) as additives. Silica and their derivatives were characterised with regard to mean pore diameter, specific surface area, pore size distribution (BET method), weight loss upon heating thermogramivemetric analysis (TGA), chemical composition Fourier transform infrared spectroscopy (FT-IR), and catalytic activities. Immobilisation yields based on the recovered lipase activity vary from 3.02 to 31.98% and the highest efficiency was attained when lipase was encapsulated using TEOS in the presence of the PEG. Further information was obtained by testing the derivatives in esterification reactions and a different reactivity profile was found. Better performance was obtained with derivatives containing lipase encapsulated within gels prepared with MTMS as precursor in the presence of PEG. This lipase preparation exhibits increased esterification activity (155 μmol g⁻¹ min⁻¹), up to of three times greater than that prepared with TEOS (52 μmol g⁻¹ min⁻¹), and almost twice that prepared with MTMS/PDMS (89 μmol g⁻¹ min⁻¹) as precursors.     

The dimerization of protochlorophyll pigments in non-polar solvents

The infrared, visible and nuclear magnetic resonance spectra of protochlorophyll a and vinylprotochlorophyll a in dry non-polar solvents (carbon tetrachloride, chloroform, cyclohexane) are presented and interpreted in terms of dimer interaction.

The infrared spectra in the 1600–1800 cm⁻¹ region clearly show the existence of a coordination interaction between the C-9 ketone oxygen function of one molecule and the central magnesium atom of another molecule. Infrared spectra in the OH stretching region (3200–3800 cm⁻¹) provide a valuable test of the water content in the samples.

The analysis of the absorption and circular dichroism spectra of protochlorophyll a and vinylprotochlorophyll a in carbon tetrachloride demonstrates the existence of a monomer-dimer equilibrium in the concentration range from 10⁻⁶ to 5 · 10⁻⁴ M. The dimerization constants are (6±2) · 10⁵ 1 · M⁻¹ for protochlorophyll a and (4.5±2) · 10⁵ 1 · M⁻¹ for vinylprotochlorophyll a at 20 °C. The deconvolution of visible spectra in the red region has been performed in order to obtain quantitative information on the dimer structure. Two models involving a parallel or a perpendicular arrangement of the associated molecules are considered.

From ¹H NMR spectra, it appears that the region of overlap occurs near ring V, in agreement with the interpretation of the infrared spectra.     

Binding of divalent copper and calcium ions to poly I

The effect ot Cu²⁺ and Ca²⁺ ions, on the ultraviolet differential (UVD) spectra of single-stranded poly I was studied and the coordination (Δε_b) and conformation (Δε_c) conponents of the spectra calculated The comparison of Δε_b and the UVD spectrum of protonated IMP leads to the conclusion that N(7) ot inosine-5'-monophosphate (IMP) is a coordinating site tor Ca²⁺ and Cu²⁺ ions on the polymer bases. The binding ot Ca²⁺ and Cu²⁺ ions causes differently directed displacements of the four absorption bands of poly I, which are observed in the wavenumber range (50-34) × 10³ cm⁻¹ The calculation of concentration dependencies tor the association constants (K“) ot Ca²⁺ and Cu²⁺ ions binding to poly I bases shows that the binding is cooperative The K“ values for the poly I + Ca²⁺ complex are two orders of magnitude lower than those for the poly 1 + Cu²⁺ complex At low ion concentrations, binding to the poly I phosphates predominates and increases the degree of the polynucleotide helicity. At higher concentrations the spectra are mainly affected by the ion binding to bases, which results in melting of the helical parts of poly I At Ca²⁺ concentrations exceeding 10⁻³ M light-scattering aggregates are formed. The degree of monomer order in them is close to that observed in multistranded helices of poly I     

Synthesis, crystal structures and magnetic studies of dicyanamide bridged two new 1D copper(II) complexes

Two new dicyanamide bridged 1D polynuclear copper(II) complexes [Cu(L¹){μ_1,5-N(CN)₂}]_n (1) [L¹H = C₆H₅C(O)NHNC(CH₃)C₅H₄N] and [Cu(L²){μ_1,5-N(CN)₂}]_n (2) [L²H=C₆H₅C(O)CHC(CH₃)NCH₂CH₂N(CH₃)₂] have been synthesised and structures of both the complexes and their crystal packing arrangements have been established by X-ray crystallography. For complex 1, a tridentate hydrazone ligand (L¹H) obtained by the condensation of benzhydrazide and 2-acetylpyridine is used, whereas a tridentate Schiff base (L²H) derived from benzoylacetone and 2-dimethylaminoethylamine is employed for the preparation of complex 2. Variable temperature magnetic susceptibility measurement studies indicate there are weak antiferromagnetic interactions with J values −0.10 and −1.41 cm⁻¹ for 1 and 2, respectively.