A novel method for the determination of carbonyl groups in cellulosics by fluorescence labeling. 3. Monitoring oxidative processes

The fluorescence-based CCOA method for determination of carbonyl group profiles in cellulosic substrates was employed to study the mechanisms of various oxidative and degradation processes involving celluloses in greater detail. The approach comprises labeling with the marker carbazole-9-carboxylic acid [2-(2-aminooxyethoxy)ethoxy]amide (CCOA), followed by gel permeation chromatography in DMAc/LiCl with fluorescence, multiangle laser light scattering, and refractive index detection. At first, the CCOA method was applied to study solutions of pulp in N-methylmorpholine-N-oxide monohydrate (NMMO), as occurring in the production of Lyocell-type fibers. NMMO is a rather strong oxidant that on one hand converts reducing end groups to carboxyl structures, thus lowering the overall carbonyl content, but generates new keto structures along the chain by nonselective oxidation on the other hand. The CCOA method allowed for the first time to distinguish the carbonyl course in different molecular weight ranges. Second, alkalization and aging of pulp, which are used in the industrial preparation of cellulose derivatives, e.g., as an element of the preripening process in viscose rayon production, were investigated. The CCOA method shows a clear reduction of the molecular weight, accompanied by a fast loss of carbonyls in the first phase, which is due to removal of low-molecular weight material by dissolution, and a slow decrease in the second phase, which is caused by further oxidation of carbonyl groups. Also here, differences in the carbonyl course in different molecular weight regions were monitored. Third, electron beaming, proposed as a means of pulp activation, was shown to decrease and narrow the molecular weight distribution, under generation of comparatively low amounts of carbonyls, which, however, are also introduced into high molecular weight, crystalline domains, as shown by a comparison of homogeneous and heterogeneous CCOA labeling approach. Finally, as the fourth application, thermal treatment of cellulose at temperatures between 105 and 165 degrees C was shown to bring about a small reduction of the molecular weight, which only at higher drying temperatures is accompanied by an introduction of carbonyls over the whole molecular weight range.     

基于NIRS法快速检测荞麦蛋白质与淀粉含量的研究

为建立近红外光谱技术测定荞麦蛋白质与淀粉含量的方法,本研究以217份荞麦样品为试验材料,采用最小二乘回归预测和交叉验证构建近红外预测模型。分析表明:前处理采用多元散射校正法(MSC),维数(Rank)分别为5和5,光谱区间6803.9~6094.2/cm所建立的荞麦蛋白质与淀粉含量模型的预测效果较好,其决定系数(R~2)分别为0.9481和0.9167,交叉验证均方根(RMSECV)分别为0.68和2.08,相对分析误差(RPD)分别为4.39和3.46,均大于3.0,外部验证相关系数均大于0.96。本试验所建立的蛋白质与淀粉含量近红外预测模型具有较高的准确度和稳健性,可用于荞麦品质的快速测定。     

Diffuse Reflectance, Near-Infrared Spectroscopic Estimation of Sugarcane Lignocellulose Components—Effect of Sample Preparation and Calibration Approach

Near-infrared spectroscopic calibrations for sugarcane lignocellulose composition (ash, lignin, and structural carbohydrates) have been developed on a total dry weight and extractives-free dry weight basis. Reference spectra were measured from crude preparations of bagasse and fibrated sugarcane stalks. Spectral interference attributed to extractives in the crude preparations adversely affected the fitting of calibrations derived from extractives-free reference data. Extractives content varied between 5 and 68 % of total dry weight and depended on the nature of the sample preparation process. Applying DOSC (direct orthogonal signal correction) to the spectra circumvented the need to physically remove these extractives from the samples prior to spectroscopic measurement. DOSC enhanced the correlation between the extractives-free reference data and the measured absorbances. Meanwhile, the correlation between the extractives reference data and the measured absorbances was attenuated. This indicated that DOSC removed the spectral contribution of the extractives. This mathematical treatment of the spectra improved the cross-validation performance of the calibrations for extractives-free lignin and some structural carbohydrates (arabinan, glucan, and xylan). The DOSC-based models explained greater than 90 % of the variance in the calibration data and led to relative standard errors of prediction under cross-validation and independent testing that were less than 10 %. Although DOSC also improved the cross-validation performance of ash and galactan calibrations, their relative standard errors under independent testing were high (>10 %). DOSC was also advantageous for total dry weight calibrations as it reduced the number of latent variables employed in the models.     

Influence of hemicellulosic derivatives on the sulfate kraft pulp strength

In this work the application of different hemicellulosic derivatives including different degrees of substitution (DS) cationic hemicelluloses and carboxymethyl hemicelluloses in sulfate kraft pulp were investigated in detail. It was found that cationic hemicelluloses and carboxymethyl hemicelluloses could improve the physical properties of hand sheets, while the cooperation of cationic hemicelluloses and carboxymethyl hemicelluloses could enhance sharply the physical properties of hand sheets. When the dosages of cationic hemicelluloses with DS of 0.37 and carboxymethyl hemicelluloses with DS of 0.35 were 1.0% and 1.0% (based on dry pulp weight), respectively, the physical properties of hand sheets was significantly improved, breaking lengthen and tear index of hand sheets increased by 21.1% and 54.6% compared with the control hand sheets without any additives added. The fiber intertexture of the hand sheets was observed by SEM. The results indicated that hemicelluloses could be used as the source for the production of wet-end additives in papermaking, which might represent an important strategy for sustainable use of the agricultural residue.     

Utilization of by-products from the tequila industry. Part 2: Potential value of Agave tequilana Weber azul leaves

The leaves of the agave plant are left in the field after harvesting the heads for tequila production. Different types of agave leaves were isolated, classified, and their content in the total plant determined. The usable fractions were collected and their properties determined. Of the total wet weight of the agave plant, 54% corresponds to the agave head, 32% corresponds to materials which could be usable for sugar and fiber production which leaves 14% of the wet plant without apparent utility. The fractions with higher total reducing sugars (TRS) content were the fresh fraction of partially dry leaves stuck to the head and the leaf bases with a TRS content of 16.1% and 13.1%, respectively. The highest TRS concentration (16-28%) is in the agave head which is used for tequila production. The leaves are 90-120 cm long and 8-12 cm wide and contain fiber bundles that are 23-52 cm long and 0.6-13 mm wide. The ultimate fiber length is approximately 1.6 mm with an average width of 25 microns. There are several types of leaf fibers that can be utilized depending on what part of the plant they come from and what product is desired. Agave leaf fibers were pulped using a soda pulping process and the pulp was hand formed into test sheets. Test sheets made from pulped agave leaf fibers had a breaking length comparable to paper made from both pine and eucalyptus fibers, but the tear index and burst index were lower than the other two papers.     

Bioelectrical impedance estimation of fat-free body mass in children and youth: a cross-validation study.

The purposes of this study were to develop and cross-validate the "best" prediction equations for estimating fat-free body mass (FFB) from bioelectrical impedance in children and youth. Predictor variables included height2/resistance (RI) and RI with anthropometric data. FFB was determined from body density (underwater weighing) and body water (deuterium dilution) (FFB-DW) and from age-corrected density equations, which account for variations in FFB water and bone content. Prediction equations were developed using multiple regression analyses in the validation sample (n = 94) and cross-validated in three other samples (n = 131). R2 and standard error of the estimate (SEE) values ranged from 0.80 to 0.95 and 1.3 to 3.7 kg, respectively. The four samples were then combined to develop a recommended equation for estimating FFB from three regression models. R2 and SEE values and coefficients of variation from these regression equations ranged from 0.91 to 0.95, 2.1 to 2.9 kg, and 5.1 to 7.0%, respectively. As a result of all cross-validation analyses, we recommend the equation FFB-DW = 0.61 RI + 0.25 body weight + 1.31, with a SEE of 2.1 kg and adjusted R2 of 0.95. This study demonstrated that RI with body weight can predict FFB with good accuracy in Whites 10-19 yr old.     

Understanding non-enzymatic aminophospholipid glycation and its inhibition. Polar head features affect the kinetics of Schiff base formation

Non-enzymatic aminophospholipid glycation is an especially important process because it alters the stability of lipid bilayers and interferes with cell function and integrity as a result. However, the kinetic mechanism behind this process has scarcely been studied. As in protein glycation, the process has been suggested to involve the formation of a Schiff base as the initial, rate-determining step. In this work, we conducted a comparative kinetic study of Schiff base formation under physiological conditions in three low-molecular weight analogues of polar heads in the naturally occurring aminophospholipids O-phosphorylethanolamine (PEA), O-phospho-DL-serine (PSer) and 2-aminoethylphenethylphosphate (APP) with various glycating carbonyl compounds (glucose, arabinose and acetol) and the lipid glycation inhibitor pyridoxal 5'-phosphate (PLP). Based on the results, the presence of a phosphate group and a carboxyl group in α position respect to the amino group decrease the formation constant for the Schiff base relative to amino acids. On the other hand, esterifying the phosphate group with a non-polar substituent in APP increases the stability of its Schiff base. The observed kinetic formation constants of aminophosphates with carbonyl groups were smaller than those for PLP. Our results constitute an important contribution to understanding the competitive inhibition effect of PLP on aminophospholipid glycation.     

Characterization of Encapsulated Flavor Systems by NIR and Low-field TD-NMR: A Chemometric Approach

A quantitative method for measuring simultaneously the flavor and water contents in model spray-dried flavor delivery systems was developed using spectroscopic techniques and chemometrics. Nine encapsulated systems were prepared, consisting of a solid carrier (maltodextrin and gum arabic) and varying the amounts of water and flavor. The model flavors used in this work were a hydrophobic (limonene) and a more hydrophilic (2,5-dimethylpyrazine) single components. Near-infrared (NIR) and low-field time-domain nuclear magnetic resonance (low field TD-NMR) data were acquired on each system and analyzed using multivariate chemometric techniques to develop optimal prediction models. Partial least squares regression models showed good predictive ability, with coefficients of determination (R²) between 0.81 and 1.00 and low root mean square error of cross-validation values compared to the range of concentrations. The predictive ability of the chemometric models computed using the NIR spectra improved significantly when data were pre-processed using multiplicative signal correction. The development of good prediction models (i.e., robust models resulting in accurate predictions for water and flavor content) from the NMR relaxation data spectra was successful only for the hydrophobic limonene systems, yielding prediction models whose performance was better than the models obtained using the NIR data. Overall, NIR spectroscopy and NMR relaxometry were identified as complementary techniques rather than competitive methods in the characterization of encapsulated flavor systems.     

The assessment of chromophores in bleached cellulosic pulps employing UV-Raman spectroscopy

UV-Resonance Raman (UV-RR) coupled with UV-visible Diffuse Reflectance (UV-vis DR) spectroscopy was applied to a solid-state study of chromophores in Eucalyptus globulus kraft cellulosic pulps bleached by chlorine dioxide and hydrogen peroxide. The UV-RR spectra were acquired at 325 nm laser beam excitation, which was shown to be appropriate for selective analysis of chromophore structures in polysaccharides. The proposed approach allowed the monitoring of chromophores in pulps and to track the extent of polysaccharide oxidation. However, precaution was suggested while performing a quantitative analysis of chromophores at the characteristic band of ∼1600 cm⁻¹ because of charge transfer complexes (CTCs) that exist in the pulp. These CTCs can affect the intensity of the aforementioned band by diminishing the conjugate state in the chromophore moieties. The amount of carbonyl and carboxyl groups in polysaccharides correlated with the intensity of the band at 1093 cm⁻¹. The analysis of UV-RR spectra revealed xylan as an important source of chromophores in eucalypt kraft pulp.     

Anticancer thiopyrano[2,3-d][1,3]thiazol-2-ones with norbornane moiety. Synthesis, cytotoxicity, physico-chemical properties, and computational studies

A series of novel 9-substituted-3,7-dithia-5-azatetracyclo[9.2.1.0(2,10).0(4,8)]tetradecen-4(8)-ones-6 have been synthesized by a stereoselective hetero-Diels-Alder reaction of 5-ylidene-4-thioxo-2-thiazolidone derivatives with norbornene-2. All the compounds have been evaluated for antitumor activity in in vitro human tumor cell lines, and 10 of them possessed significant and selective cytotoxicity (MGM logGI50 approximately -4.17 to -4.98, for individual cell lines logGI50 up to -8). COMPARE analyses of differential growth inhibition patterns of compounds at the GI50 level showed high correlations with some of the antitubulin agents. The lipophilicity of the compounds was studied by RP-TLC and found to correlate well with calculated logP values. Docking and structure-activity relationship studies produced seven QSAR models with 2 or 3 variables, with correlation coefficients r2>0.9 and leave-one-out cross-validation correlation coefficients, q2>0.8.     

Photoelectron spectra of complexes of Na and La with N-acetylalanine and N-acetylvaline

X-ray photoelectron spectra of the bioinorganic complexes of Na and La with N-acetylalanine and N-acetylvaline have been measured. It has been found that the spectra of the O 1s core level in the complexes of Na with these amino acids are very different from those in the complexes of La with the same amino acids. The results indicate that in the complexes of La with N-acetylalanine and N-acetylvaline, both the oxygen atoms from the carboxyl group and the oxygen atoms from the carbonyl group of the amino acids will directly coordinate to the La ion, whereas only the oxygen atoms from the carboxyl group of the amino acids can directly coordinate to the Na ion in the complexes of Na with N-acetylalanine and N-acetylvaline.     

食用调和油中花生油含量的近红外光谱分析

采用偏最小二乘法(PLS)等方法建立了食用调和油中花生油含量定量分析的近红外光谱定标模型。采集食用调和油样品在4 000 cm-1~10 000 cm-1范围内的近红外漫反射光谱,光谱经一阶导数处理后,采用偏最小二乘法建立样品中花生油含量的定标模型,并用Leave-one-out内部交叉验证法对模型进行验证。模型相关系数为0.99961,校正均方根RMSEC为0.830%。比较不同光谱预处理方法对定标模型的影响,结果表明一阶导数Corr.coeff最好。采用不同的化学计量学方法建立的定标模型中以偏最小二乘回归法最理想。     

Assessment of the orientation and conformation of pigments in protein binding sites from infrared difference spectra

Time resolved FTIR difference spectroscopy (DS) has been used to study photosystem I (PSI) with the disubstituted 1,4-naphthoquinones acequinocyl (AcQ) and lapachol (Lpc) incorporated into the A₁ binding site. AcQ is a 2-acetoxy-3-dodecyl-1,4-naphthoquinone, Lpc is a 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone. To assess whether the experimental spectra are specific to different orientations of the quinone and their substitutions ONIOM-type QM/MM vibrational frequency calculations were undertaken for various orientations of the pigments and side-chain conformations in the A₁ binding site.Comparison of calculated and experimental spectra for the reduced species (semiquinone anion) suggests that the orientation for the naphthoquinone ring in the binding site and specific side-chain conformations can be identified based on the spectra. In native PSI phylloquinone (PhQ) in the A₁ binding site binds with its phytyl chain ortho to the hydrogen bonded carbonyl group. This is not found to be the case for the hydrocarbon tail of AcQ, which is meta to the H-bonded carbonyl group. In contrast, Lpc in PSI binds with its hydrocarbon tail also ortho to the H-bonded carbonyl group. Furthermore, comparison of calculated and experimental spectra indicates which conformations the acetoxy group of AcQ and the hydroxy group of Lpc adopt in the A₁ binding site.     

Quantitative structure-activity relationship study of bitter di- and tri-peptides including relationship with angiotensin I-converting enzyme inhibitory activity.

Bitterness represents a major challenge in industrial application of food protein hydrolysates or bioactive peptides and is a major factor that controls the flavor of formulated therapeutic products. The aim of this work was to apply quantitative structure-activity relationship modeling as a tool to determine the type and position of amino acids that contribute to bitterness of di- and tri-peptides. Datasets of bitter di- and tri-peptides were constructed using values from available literature, followed by modeling using partial least square (PLS) regression based on the three z-scores of 20 coded amino acids. Prediction models were validated using cross-validation and permutation tests. Results showed that a single-component model could explain 52 and 50% of the Y variance (bitterness threshold) of bitter di- and tri-peptides, respectively. Using PLS regression coefficients, it was determined that hydrophobic amino acids at the carboxyl-terminus and bulky amino acid residues adjacent to the carboxyl terminal are the major determinants of the intensity of bitterness of di- and tri-peptides. However, there was no significant (p > 0.05) correlation between bitterness of di- and tri-peptides and their angiotensin I-converting enzyme-inhibitory properties.     

A comparative study of the effect of refining on organosolv pulp from olive trimmings and kraft pulp from eucalyptus wood

This paper examines the influence of the degree of refining of different pulps, produced from olive trimmings and eucalyptus wood, on various physical properties. Corresponding pulps were obtained by means of different cooking processes. Pulp from olive trimmings was obtained by means of an organosolv process and pulp from eucalyptus was obtained by means of a kraft process. Pulp from olive trimmings exhibited a lower specific surface area, water retention volume, breaking length, stretch and burst index, but a higher porosity, than eucalyptus pulp. On the other hand, the same degree of refining was achieved with less energy for olive pulp than for eucalyptus pulp. Mixed pulp from olive trimmings and eucalyptus provided paper sheets with acceptable physical properties but with reduced refining energy costs relative to eucalyptus pulp alone.     

Dealing with clustered samples for assessing map accuracy by cross-validation

Mapping of environmental variables often relies on map accuracy assessment through cross-validation with the data used for calibrating the underlying mapping model. When the data points are spatially clustered, conventional cross-validation leads to optimistically biased estimates of map accuracy. Several papers have promoted spatial cross-validation as a means to tackle this over-optimism. Many of these papers blame spatial autocorrelation as the cause of the bias and propagate the widespread misconception that spatial proximity of calibration points to validation points invalidates classical statistical validation of maps. We present and evaluate alternative cross-validation approaches for assessing map accuracy from clustered sample data. The first method uses inverse sampling-intensity weighting to correct for selection bias. Sampling-intensity is estimated by a two-dimensional kernel approach. The two other approaches are model-based methods rooted in geostatistics, where the first assumes homogeneity of residual variance over the study area whilst the second accounts for heteroscedasticity as a function of the sampling intensity. The methods were tested and compared against conventional k-fold cross-validation and blocked spatial cross-validation to estimate map accuracy metrics of above-ground biomass and soil organic carbon stock maps covering western Europe. Results acquired over 100 realizations of five sampling designs ranging from non-clustered to strongly clustered confirmed that inverse sampling-intensity weighting and the heteroscedastic model-based method had smaller bias than conventional and spatial cross-validation for all but the most strongly clustered design. For the strongly clustered design where large portions of the maps were predicted by extrapolation, blocked spatial cross-validation was closest to the reference map accuracy metrics, but still biased. For such cases, extrapolation is best avoided by additional sampling or limitation of the prediction area. Weighted cross-validation is recommended for moderately clustered samples, while conventional random cross-validation suits fairly regularly spread samples.     

Experimental and theoretical studies of vacuum-ultraviolet electronic circular dichroism of hydroxy acids in aqueous solution

The electronic circular dichroism (ECD) spectra of three L-hydroxy acids (L-lactic acid, (+)-(S)-2-hydroxy-3-methylbutyric acid, and (-)-(S)-2-hydroxyisocaproic acid) were measured down to 160 nm in aqueous solution using a vacuum-ultraviolet ECD spectrophotometer. To assign the two positive peaks around 210 and 175 nm and the one negative peak around 190 nm in the observed spectra, the ECD spectrum of L-lactic acid was calculated using time-dependent density functional theory (DFT) for the optimized structures by DFT and a continuum model. The observed ECD spectrum was successfully reproduced as the average spectrum for four optimized structures with seven water molecules that localized around the COO(-) and OH groups of L-lactic acid. The positive peak around 210 nm and the negative peak around 185 nm in the calculated spectrum were attributable to the nπ* transition of the carboxyl group, with the latter peak also being influenced by the ππ* transition of the carboxyl group; however, the positive peak around 165 nm involved unassignable higher energy transitions. The comparison of the calculated ECD spectra for L-lactic acid and L-alanine revealed that the network with loose hydrogen bonding around the COO(-) and OH groups is responsible for the flexible conformation of hydroxy acids and complicated side-chain dependence of ECD spectra relative to amino acids.     

Bleaching of wheat straw-rich soda pulp with xylanase from a thermoalkalophilic Streptomyces cyaneus SN32

An alkalistable endoxylanase from Streptomyces cyaneus SN32 was applied in bleaching of wheat straw enriched soda pulp. The xylanase dose of 10 IUg(-1) moisture free pulp exhibited maximum bleach boosting of soda pulp (pH 9.5-10.0) optimally at 65 degrees C after 2 h of reaction time. Pre-treatment of pulp with xylanase and its subsequent treatment with 6% hypochlorite reduced the kappa number by 8.7%, enhanced the brightness index by 3.56% and improved other paper properties such as tear index and burst index. The enzymatically-prebleached pulp when treated with 10% reduced level of hypochlorite (5.4%) gave comparable brightness of resultant hand sheets to the fully bleached pulp (6% hypochlorite).     

Comparison of the vibration mode of metals in HNO3 by a partial least-squares regression analysis of near-infrared spectra

The near-infrared (NIR) spectra of such metals as Cu(II), Mn(II), Zn(II) and Fe(III) in HNO(3) in the 700-1,860 nm region were subjected to a partial least-squares regression analysis and leave-out cross-validation to develop chemometric models. The models yielded a coefficient of determination in cross validation of 0.9744 [Cu(II)], 0.9631 [Mn(II)], 0.9154 [Zn(II)] and 0.741 [Fe(III)]. The regression coefficients for Cu(II), Mn(II) and Zn(II), but not for Fe(III), showed strong negative peaks at around 1,050-1,200 nm, a zone where spectral bands have been reported to decrease with increasing pH value. A positive peak at around 710-750 nm, which may have been due to water absorption, was observed in regression coefficients of Cu(II), Mn(II) and Zn(II) but not in Fe(III), while a negative peak was observed in that for Fe(III) at around 710-750 nm. These results indicate that the divalent cations [Cu(II), Mn(II) and Zn(II)] showed different absorption in the NIR region from the trivalent cation [Fe(III)], suggesting that the vibration mode of water, which mirrors the interaction between cations and water, may be influenced by valency.