Mixed acylation of Scots pine sawdust and impact on hydrophobicity

Abstract

Acetic–fatty esters of Scots pine sawdust (SPS) were obtained by reaction of SPS with mixtures containing acetic–fatty anhydrides and no solvent or catalyst. Such mixtures were synthesized by reaction between a carboxylic acid and acetic anhydride. The global reaction of acetic anhydride and a fatty acid yields at equilibrium a mixture of five compounds: acetic–fatty anhydride, acetic anhydride, fatty acid, acetic acid and fatty anhydride. The influence of temperature, molar ratio, reaction time and length of the fatty chain on the esterification and on the ratio of grafted acetyl/fatty acyl was investigated. Static contact angles (CAs) with water were measured over 5 min. CA values were dependent on the fatty acyl content and independent of the acetyl content. The minimum ester content of the oleoyl group required to obtain permanent water repellency was 25 mmol kg^?1. Water vapour adsorption measurements indicated that in contrast to water repellency, hydrophobicity to water vapour was correlated with the total mass acyl content.     

Application of a modified rate equation to the acetylation of wood

A modified rate equation, in which the diffusion of reagent was taken into consideration, was proposed and applied to results reported previously for the acetylation of wood. The equation was fitted more successfully to the prolonged as well as the early stage of the reaction than a common first-order rate equation. Although the conclusions were virtually unchanged, the reliability was enhanced because reaction parameters such as the rate constant, ultimate extent of the reaction, and activation energy calculated for the modified equation were based on much more data than those reported previously. The equation proposed here may be applicable not only to acetylation but to other chemical modifications of cellulosic materials in heterogeneous systems.     

Histone H4 Modification During Mouse Spermatogenesis

The core histone is composed of four proteins (H2A, H2B, H3 and H4). Investigation of the modification patterns of histones is critical to understanding their roles in biological processes. Although histone modification is observed in multiple cells and tissues, little is known about its function in spermatogenesis. We focused on the modification patterns of histone H4 during murine spermatogenesis. We demonstrated that the individual N-terminal sites of H4 show different modification patterns during the differentiation of male germ cells. The methylation pattern varied depending on the residues that were mono-, di-, or tri-methylated. All the H4 modifications were high during the meiotic prophase, suggesting that histone H4 modification plays an important role during this stage of spermatogenesis. Elongating spermatids showed increased acetylation of histone H4, which may be associated with a histone-to-protamine substitution. Our results provide further insight into the specific relationship between histone H4 modification and gene expression during spermatogenesis, which could help to elucidate the epigenetic disorders underlying male infertility.     

Postia placenta decay of acetic anhydride modified wood – Effect of leaching

Abstract

It is well established that acetylation of wood by the use of acetic anhydride is able to impart a significant degree of decay resistance. The aim of this work was to study how a standardized leaching procedure with water (EN 84) affected the degradation of acetic anhydride modified samples by the brown rot fungi Postia placenta compared to no leaching prior to incubation. Three different levels (low, medium, and high) of acetic anhydride modified Southern yellow pine (SYP; Pinus spp.) were tested. The samples were harvested after 4 and 28 weeks. We compared changes in mass loss, wood moisture content, fungal DNA, and gene expression from five genes. If leaching changes the acetylated samples and makes them more susceptible for fungal deterioration, the expected effect would be higher levels of these parameters. Generally, leaching resulted in few differences between leached and nonleached samples at low levels of acetylation, while no changes were found for the highest acetylation level. No differences were found in gene expressions after 28 weeks. The possible protection of acetylated wood against oxidative fungal degradation is suggested to be interpreted in combination with the lowered wood moisture content.     

低取代度糯玉米淀粉醋酸酯的制备

以糯玉米淀粉为原料,醋酸酐为乙酰化试剂,氢氧化钠为催化荆,硫酸钠为膨胀抑制荆,制备了低取代度糯玉米淀粉醋酸酯。考察了醋酸酐用量、膨胀抑制刺用量、pH值、反应温度、反应时间等因素对糯玉米淀粉醋酸酯乙酰基含量和反应效率的影响。试验结果表明,醋酸酐用量、硫酸钠用量、pH值、反应温度和反应时间对糯玉米淀粉醋酸酯的取代度有影响。通过试验得到制备低取代度糯玉米淀粉醋酸酯的较佳工艺条件为：pH值9．0,反应温度30℃,反应时间60min,硫酸钠用量2％（以淀粉干基质量计）。     

Acetylation of intact white rice grains to alter the physicochemical properties

The effect of acetylation of milled rice grains of selected varieties (TDK 8, YRW 4, Reiziq, Amber 33, and SHZ 2) with varying apparent amylose contents (3.8–26.6%) on their physicochemical properties was investigated. Milled rice samples were treated with different acetic anhydride concentrations (0.004–0.04 g per 100 g of milled rice samples in 225 mL of water). Results showed that glutinous (TDK 8), very low amylose (YRW 4) and low amylose containing varieties (Reiziq) were prone to acetylation even with 0.004 g of acetic anhydride. X-ray diffraction patterns showed an increase in the crystallinity in acetylated samples and formation of V-type crystals, suggesting the possible interaction of acetic anhydride with starch. Acetylation of rice grains resulted in reduced peak and final viscosities and gel strength, particularly in glutinous (TDK 8) and very low amylose (YRW 4) rice. Differential calorimetric study showed that acetic anhydride treatment resulted in reduced thermal transition temperatures and enthalpy of all varieties. Although increase in the retrogradation thermal temperatures was observed, the enthalpy of retrogradation was reduced with increasing acetylation, suggesting that the extent of starch retrogradation was lower in all varieties with more prominent reduction in the glutinous type. Furthermore, the texture of cooked acetic anhydride treated rice grains was less hard and showed more adhesiveness. This study demonstrated that the acetylation of rice grains (instead of flour) was successfully achieved, showing the potential of applying acetylation to alter the textural, pasting, thermal and retrogradation properties of rice.     

乙酰化糯玉米二淀粉甘油酯制备工艺研究

采用醋酸酐和环氧氯丙烷对糯玉米淀粉进行双重变性制备乙酰化二淀粉甘油酯。通过单因素试验,研究了pH值、反应温度、环氧氯丙烷用量、醋酸酐用量、交联反应时间、乙酰化反应时间对冷粘度的影响。通过Box-Behnken六因素三水平试验确定制备乙酰化二淀粉甘油酯的最佳工艺参数为：pH值为9.91,反应温度为43.2℃,环氧氯丙烷用量0.26%,醋酸酐用量7.94%,交联反应时间为4.9 h,乙酰化反应时间为1.4 h。     

Chemical modification of wood by anhydrides without solvents or catalysts

Acetylated, propionylated, butyrylated, isobutyrylated, and hexanoylated woods were prepared at several temperatures. The reaction rate, dimensional stability, and changes in the ratios of specific gravity and dimensions in the tangential and radial directions were estimated. The reaction rate of propionylation was slow at temperatures under 90°C but increased with the temperature. The butyrylated, isobutyrylated, and hexanoylated woods showed little or no weight percent gain (WPG) and little or no antiswelling efficiency (ASE) below 110°C even for 24h, but they achieved significant WPG and ASE values at 140°C with a longer reaction time. The acetylated, propionylated, and butyrylated woods showed almost the same values for dimensional stabilization efficiency based on WPG (DSE). The specific gravity and dimensions ratios for acetylated, propionylated, and butyrylated woods compared to those of untreated wood increased with an increase in WPG.     

乙酰化木材的制备及其热塑性研究

利用乙酰化改性反应使木材获得热塑性，利用ＩＲ，ＤＳＣ，ＳＥＭ等对乙酰化木材的化学结构及热塑性进行了研究和表征。常规乙酰化方法不能使木材热塑化，而经三氟乙酸预处理制得的乙酰化木材在２９０－３００℃熔融，可在１１０－１３０℃单独或与其他合成高聚物共混热压成半透明薄片。