Sweet like chocolate

A new crystalline form of αβ‐d ‐lactose prepared by oven drying a concentrated aqueous solution of d ‐lactose is a lesson in the power of observation and the rigorous analysis of powder samples.     

含乳糖酸修饰的多壁碳纳米管复合载药体系的合成及表征

以聚乙烯亚胺(PEI)修饰的多壁碳纳米管(PEI-CNT)为模板,利用异硫氰酸荧光素(FITC)和乳糖酸(LA)对其表面进行修饰,合成乳糖酸修饰的PEI-CNT复合载体,并负载抗肿瘤药物盐酸阿霉素(DOX),使其成为具有靶向功能的新型抗肿瘤药物载体。采用核磁共振(1 HNMR)、透射电镜、共聚焦显微镜及流式细胞仪等测试手段分析载体的结构和性质。载药复合体系在酸性条件下的体外药物释放速率明显高于中性条件下的,同时该复合载药体系对肝癌细胞(SMMC-7721)具有一定的靶向性。     

受乳糖启动子控制的基因表达过程的优化

借助于ＳＤＳ－聚丙烯酰胺凝胶电泳分析方法，对乳糖诱导的由乳糖启动子控制的大肠杆菌ＲＮＡ聚合酶σ７０因子基因表达过程进行了优化研究．结果表明，含此融合基因的大肠杆菌菌株ＢＬ２１（ＤＥ３）ｐＧＥＭＤ的生长量达到ＯＤ６００ｎｍ＝１．０时，用终浓度为０．０８％的乳糖进行连续５ｈ的诱导，可使大肠杆菌ＲＮＡ聚合酶σ７０因子基因的表达量达到最大，并达到ＩＰＴＧ同样的诱导效果．流加低浓度的乳糖溶液能增加σ７０因子的合成量，但是促进作用不很显著．     

Ultrasound assisted crystallization for the recovery of lactose in an anti‐solvent acetone

Continuous worldwide increase in high‐scale production of dairy products leads to the constant generation of vast amounts of liquid by‐product, whey. Disposal of liquid whey is costly due to its high biological oxygen demand (BOD) and water content. More than 90% of whey BOD is due to lactose. Recovery of lactose from whey solves both the problems of improving economics of whey utilization and pollution reduction as lactose recovery itself can reduce BOD of whey by more then 80%. Commercial effluent treatment techniques focus on degradation rather than recovery of useful by‐products like lactose. Also, these techniques are time consuming and hence not effective enough. Sonocrystallization is the use of power ultrasound to control the crystallization process during the nucleation phase. In the present study, the process of lactose crystallization has been studied for the recovery of lactose from reconstituted lactose solutions with the aid of ultrasound, in the presence of ‘acetone’, as an anti‐solvent. The crystallization is found to be completed with excellent yields in the range of 80 – 92% within 4 minutes of sonication. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Purification and properties of a β-galactosidase with potential application as a digestive supplement

Functional-based screening of crude β-galactosidase activities from 42 yeast strains resulted in the selection of a single enzyme of potential interest as a digestive supplement. β-Galactosidase produced by Kluyveromyces marxianus DSM5418 was purified to homogeneity by a combination of gel filtration, ion-exchange, and hydroxylapatite chromatographies. The denatured (123 kDa) and native molecular masses (251 kDa) suggest that the enzyme is a homodimer. The optimum pH and temperature of the purified enzyme were 6.8 and 37°C, respectively. The unpurified β-galactosidase in particular displayed a high level of stability when exposed to simulated intestinal conditions in vitro for 4 h. Matrix-assisted laser desorption ionization mass sectrometry analysis revealed that the enzyme's trypsin-generated peptide mass fingerprint shares several peptide fragment hits with β-galactosidases from Kluyveromyces lactis. This confirms the enzyme's identity and indicates that significant sequence homology exists between these enzymes.     

Physicochemical characteristics of commercial lactases relevant to their application in the alleviation of lactose intolerance

Selected microbial lactases are used to treat lactose intolerance. A series of experiments were carried out in vitro in order to determine the likely relative suitability of four major commercial lactase products used in this regard. The lactases displayed between 55 and 61% of maximum activity at 37°C and significant acitvity between pH3.0 and 6.5. They retained between 0 and 65% of original activities after exposure to full simulated digestive tract conditions for 6 h. All four enzymes proved to be particularly acid sensitive and only two products were enteric coated. The products demonstrated varying ability to hydrolyze lactose under simulated digestive tract conditions. The most effective product hydrolyzed 2.7 g lactose per capsule, suggesting that consumption of several capsules, as opposed to the usually recommended one or two, would be required to hydrolyze the entire 12 g lactose load characteristic of a dairy-based meal. All enzymes were substantially pure and displayed similar kinetic properties and molecular weights. None appeared ideally suited for use in the alleviation of lactose intolerance. The findings may in part explain the variability and often disappointing results previously reported for lactase-based clinical trials and will provide comparative baseline data against which candidate second-generation lactases may be assessed.     

Novel Boronlectins Based on Bispyridium Salt with a Flexible Linker: Discriminative Sensing of Lactose and Other Monosaccharides and Disaccharides in Aqueous Solution

N,N‐Di‐2‐picolylamine (DPA)‐derived diboronic acid receptors (NHBAs) with a flexible linker were designed and synthesized in this study, and two‐component sensing ensembles based on cationic NHBAs and an anionic fluorescent indicator 8‐hydroxypyrene‐1,3,6‐trisulfonic acid trisodium salt (HPTS) were successfully developed for both monosaccharides and disaccharides sensing. The dibranched ortho‐substituted receptor NHoBA exhibited unexpected selectivity towards lactose among five disaccharides used. The discrimination of five disaccharides and six monosaccharides was finally achieved by the integrated sensor array through linear discriminant analysis (LDA).     

乳糖接枝聚乙烯亚胺壳聚糖的合成

本文通过马来酸酐化的壳聚糖,在2-NH2上引进分子量为2000的支链型聚乙烯亚胺,再用乳糖与聚乙烯亚胺的氨基反应,得到了乳糖接枝的聚乙烯亚胺化的壳聚糖。目标产物用1H NMR进行了表征。该共聚物在水中有很好的溶解性。     

Effect of process parameters on crystal size and morphology of lactose in ultrasound‐assisted crystallization

α‐lactose monohydrate is widely used as a pharmaceutical excipient. Drug delivery system requires the excipient to be of narrow particle size distribution with regular particle shape. Application of ultrasound is known to increase or decrease the growth rate of certain crystal faces and controls the crystal size distribution. In the present paper, effect of process parameters such as sonication time, anti‐solvent concentration, initial lactose concentration and initial pH of sample on lactose crystal size, shape and thermal transition temperature was studied. The parameters were set according to the L₉‐orthogonal array method at three levels and recovered lactose from whey by sonocrystallization. The recovered lactose was analyzed by particle size analyzer, scanning electron microscopy and differential scanning calorimeter. It was found that the morphology of lactose crystal was rod/needle like shape. Crystal size distribution of lactose was observed to be influenced by different process parameters. From the results of analysis of variance, the sonication time interval was found to be the most significant parameter affecting the volume median diameter of lactose with the highest percentage contribution (74.28%) among other parameters. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Sweet Vector for Gene Delivery: the Sugar Decoration of Polyplexes Reduces Cytotoxicity with a Balanced Effect on Gene Expression

The use of sugar‐functionalized polyplexes as a nonviral gene delivery vector with lower cytotoxicity than the well‐known polymeric carrier branched polyethyleneimine (BPEI) is investigated. The substitution of primary amine groups in the BPEI chains with lactose residues leads to larger polyplexes, presumably due to the higher amount of polymer required to complete DNA condensation. Nevertheless, the sugar functionalization substantially reduces the cytotoxicity of the assemblies. The nanocomplexes are taken up by the cells to a greater extent, whereas the levels of gene expression are maintained compared to those obtained using BPEI, which is known for its excellent transfection efficiency. Accordingly, the preparation of lower‐cytotoxicity polyplexes while maintaining gene expression, which is highly relevant to the field, is demonstrated.