Preparation of glucosamine by hydrolysis of chitosan with commercial α-amylase and glucoamylase*

Objective: In order to overcome the defects of chemical hydrolysis approach to prepare glucosamine, an enzymatic hydrolysis method was developed. Methods: Glucosamine was prepared by hydrolyzing chitosan, employing α-amylase initially, and subsequently, glucoamylase. Results: The optimal hydrolyzing conditions were as follows: reaction time, 4 h; pH, 5.0; temperature, 50 °C; and, α-amylase, 80 U/g for the initial reaction. Subsequently, glucoamylase was added in the presence of α-amylase. The optimal reaction conditions were found to be: reaction time, 8 h; pH, 4.5; temperature, 55 °C; and, glucoamylase, 4 000 U/g. The hydrolysates were subject to filtrating, concentrating to about 20% (w/w), precipitating with five volumes of ethanol, and drying at 60 °C for 2 h. The content and the yield of glucosamine in the dried precipitate were 91.3% (w/w) and 86.2% (w/w), respectively. Conclusions: The method developed in this study is a promising option in the preparation of glucosamine

TiO2-functionalized mesoporous materials for sensitive analysis of multi-phosphopeptides

Protein phosphorylation as one of the most important post-translational modifications in mammalian cells regulates numerous biological processes. Here we propose a novel strategy for the selective isolation and sensitive analysis of multi-phosphopeptides based on TiO2-gratfed mesoporous materials, in which MCM-41 and SBA-15 were chosen as the hard templates. The commercialized IMAC and TiO2 nanopartices were further investigated in the phosphopeptide analysis for comparison. The enrichment efficiency was evaluated and measured by MALDI-TOF mass spectrometry. The results indicated that both TiO2-SBA-15 and TiO2-MCM-41 exhibited the preferential affinity to multi-phosphopeptides compared with the other two widely used strategies. The mesoporous TiO2 based protocol showed highly selective and sensitive properties, where phosphopeptides could be identified at femtomole

What determines levels of passive smoking in children with asthma?

BACKGROUND: Children with parents who smoke are often exposed to high levels of environmental tobacco smoke, and children with asthma are particularly susceptible to the detrimental effects of passive smoking. Data were collected from parents who smoke and from their asthmatic children. The families are currently taking part in a randomised controlled trial to test an intervention designed to reduce passive smoking in children with asthma. This paper reports on the baseline data. Questionnaire data and cotinine levels were compared in an attempt to assess exposure and to identify factors which influence exposure of the children. The aim of the study was to identify the scope for a reduction in passive smoking by these children. METHODS: A sample of 501 families with an asthmatic child aged 2-12 years was obtained. Factors influencing passive smoking were assessed by interviewing parents. Cotinine levels were measured from saliva samples using gas liquid chromatography with nitrogen phosphorous detection. RESULTS: Cotinine levels in children were strongly associated with the age of the child, the number of parents who smoked, contact with other smokers, the frequency of smoking in the same room as the child, and crowding within the home. Parental cotinine levels, the amount smoked in the home, and whether the home had a garden also exerted an independent effect on cotinine levels in the children. CONCLUSIONS: Many children are exposed to high levels of environmental tobacco smoke and their cotinine levels are heavily dependent upon proximity to the parent who smokes. Parents who smoke have a unique opportunity to benefit their child's health by modifying their smoking habits within the home. 



Significance of partial substitution of carbon by nitrogen on strengthening and toughening mechanisms of high nitrogen Fe-15Cr-1Mo-C-N martensitic stainless steels

We elucidated the significance of partial substitution of C by N in three high nitrogen Fe-15Cr-1Mo-C-N martensitic stainless steels (MSSs), and particularly its influence on microstructural features and the strength-toughness balance. The results show that partial substitution of C by N avoided the formation of coarse intergranular carbides and caused significant changes in the type of carbonitrides from M23C6 to M23C6+M2N and finally to M2N. Meanwhile, partially replacing C by N first increased and then decreased the effective grain size, the fraction of retained austenite, and the plate martensite, while the variations of the amount of carbonitrides and dislocation density were just the opposite. The microstructural evolutions with varying (C+N) contents played a crucial role in determining the overall properties: the 0.35C-0.37N steel exhibited an improved impact toughness (similar to 86.1 J), which was 2 or 3 times higher than those of 0.50C-0.16N and 0.20C-0.54N steels, even at a strength level of over 2 GPa. The contributions of partial substitution of C by N on the strengthening mechanisms of MSSs were also systematically revealed by combining the experimental and theoretical data. (C) The Minerals, Metals & Materials Society and ASM International 201