Determination of chitin and protein contents during the isolation of chitin from shrimp waste

Accurate determination of chitin and protein contents in crustacean biomass and the intermediate products during the industrial isolation of chitin cannot be made directly from the total nitrogen content, unless the appropriate corrections are applied. This method, however, is affected by the presence of other nitrogen-containing chemical species that are formed endogenously or by the action of microorganisms during the handling of the sample. Therefore, an alternative rapid method to estimate the contents of these components can be very useful both in research and in various fields of application. An original method has been developed to address this problem. The method consists of the development of a set of equations based on the stoichiometric contents of nitrogen of chitin and protein whereby the amounts of each component can be estimated from the value of the total nitrogen content, provided the rest of the proximate composition of the sample is accurately known. In order to validate the procedure, a set of model mixtures of pure chitin and protein concentrate in the solid state, both extracted from shrimp head waste, are used. Excellent agreement between the predicted and real values of chitin and protein are obtained (R2=0.98, slope=0.90). When the proposed method is tested in the analysis of real samples obtained from five different processing protocols of pretreatment of raw shrimp head, it is found that in general the values of protein and chitin contents throughout the various stages of the process vary as expected. [GRAPH: SEE TEXT] Variation of the measured total nitrogen versus calculated stoichiometric total nitrogen of the chitin-protein mixtures.     

A new and fast extraction method for the determination of priority phenols from marine sediments by liquid chromatography

A new and fast method for the determination of priority phenols in marine sediment samples by high-performance liquid chromatography using microwave-assisted micellar extraction is optimized. This study is carried out using the nonionic surfactants polyoxyethylene 9 lauryl ether (polidocanol) and genapol X-080 as extractants. Parameters studied include surfactant concentration, solution pH, extraction time, and power. Once the method is optimized, it is applied to different spiked marine sediments from of the Canary Islands coastlines (Spain). The results obtained indicate that a power irradiation of 500 W for 2 min achieved the best extraction efficiency (approximately 100% recovery) and less than 10% relative standard deviation. Detection limits are obtained in the 2-20 microg/g range for the phenols studied. Finally, the proposed method provides a simple, fast, and organic solvent-free procedure to analyze phenols from marine sediment samples.     

The spinning,structure, and properties of cellulose/chitin blend filaments through HWM method

The aim of this paper is the preparation and characterization of cellulose/chitin blend filaments over the experimental blend ratio scope i.e., 2.89 and 6.46% (w/w) chitin content through high wet modulus (HWM) procedure. The spinnability of the invested solutions was found to vary in the following order: chitin < cellulose < 9.5:0.5 blend < 9:1 blend < 8:2 blend < 5:5 blend (9:1 means the mass ratio of cellulose to chitin, so does 9.5:0.5, 8:2, and 5:5). The cross‐section of the blend filaments is of chrysanthemum shape. It was shown through the SEM photographs that there existed grooves on the surface of filaments, which became coarse with increase in chitin content. Based on the data from X‐ray, sonic velocity, intensity, and hygroscopicity, it is concluded that the degree of crystallinity, dry and wet intensity modulus, degree of orientation, and regain rate of the filaments decreased with increase in chitin content in the experiment scope. The mechanical properties of the blend filaments are much higher than those of Crabyon fiber and normal viscose filaments, which proves that the HWM method is an efficient way of preparing cellulose/chitin blend filaments with satisfactory mechanical properties and processing property. The blend filaments prepared have an effective biostatic effect on Staphylococcus aureus, Escherchia coli, and Corinebaterium michiganence according to different testing standards. Copyright © 2009 John Wiley & Sons, Ltd.     

A new method for stable lead isotope extraction from seawater

A new technique for stable lead (Pb) isotope extraction from seawater is established using Toyopearl AF-Chelate 650 M^® resin (Tosoh Bioscience LLC). This new method is advantageous because it is semi-automated and relatively fast; in addition it introduces a relatively low blank by minimizing the volume of chemicals used in the extraction. Subsequent analyses by HR ICP-MS have a good relative external precision (2σ) of 3.5‰ for ²⁰⁶Pb/²⁰⁷Pb, while analyses by MC-ICP-MS have a better relative external precision of 0.6‰. However, Pb sample concentrations limit MC-ICP-MS analyses to ²⁰⁶Pb, ²⁰⁷Pb, and ²⁰⁸Pb. The method was validated by processing the common Pb isotope reference material NIST SRM-981 and several GEOTRACES intercalibration samples, followed by analyses by HR ICP-MS, all of which showed good agreement with previously reported values.     

共振散射光谱法测定聚丙烯酰胺浓度

在醋酸介质中,聚丙烯酰胺(PAM)与次氯酸钠溶液作用生成疏水性的氯酸胺微粒,该微粒体系在480 nm处产生强的共振散射峰.PAM的质量浓度在1.6～80.0 mg/L范围内与480 nm处共振散射光强度成线性关系,检出限为0.30 mg/L PAM.研究了共存物质对共振散射光谱法测定PAM浓度的影响,方法的选择性较好,应用于合成废水中PAM的测定,结果满意.     

A simple and affordable method for high-throughput DNA extraction from animal tissues for polymerase chain reaction

We have developed a very simple and inexpensive method for high-throughput DNA extraction from animal tissues. The procedure contains three steps (digestion, heating, and centrifugation) and it is compatible with the 96-well plate format commonly used in polymerase chain reaction (PCR) amplifications. The duration for processing a plate is about 1.5 h; therefore, one researcher can isolate DNA from up to 1000 samples during a single workday. A small piece of tissue (ca. 10-20 mg) yields enough template for at least 50-70 PCR amplifications, as demonstrated by using the processed samples as templates successfully for long distance PCR, multiplex PCR, and randomly amplified polymorphic DNA (RAPD) assay. The application of our method is expected to facilitate studies that require high-throughput DNA isolation for PCR amplification, such as genotyping by microsatellites for mapping and genetic diversity studies, as well as mutant screening in zebrafish.     

Structural features of chitin from Aral crustaceans and use of chitosans based on it

Structural features of chitin from Aral crustaceans and chitosan based on it are examined using x-ray diffraction and IR spectroscopy. Their biological activities on encapsulated cotton seeds are determined.Institute of Polymer Chemistry and Physics, Academy of Sciences of the Republic of Uzbekistan, Tashkent, 700128, ul. A. Kodirii, 76, fax 144 26 61. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 97–99, March–April, 2000.     

Synthetic modifications of chitin and chitosan as multipurpose biopolymers: A review

Chitin and chitosan are well-thought-out multipurpose biopolymers. Chitosan which is deacetylated chitin is useful than chitin and is biomaterial of great interest. Regardless of its biodegradability, chemical modifications suggest due to the amino side reactivity, helps to impart it other great qualities. Herein, we discuss the preparative methods of synthetically modified derivatives, some are commercially available. This review shields the literature from last few decades.     

薯蓣皂甙提取新工艺

盾叶薯蓣是一种常用的中草药,又名黄姜、火头根,是我国特有甾体激素类药源植物,也是世界上薯蓣皂甙元含量最高的资源植物[1].其所含薯蓣皂甙元具有增强性功能、抗衰老和治疗心血管疾病、保护肝脏、抑制癌细胞增殖、治疗骨质疏松等功效,是合成各种避孕药和甾体激素类药物的主要原料[2-3].     

A new method for fast and accurate derivation of molecular conformations

During molecular simulations, three-dimensional conformations of biomolecules are calculated from the values of their bond angles, bond lengths, and torsional angles. In this paper we study how to efficiently derive three-dimensional molecular conformations from the values of torsional angles. This case is of broad interest as torsional angles greatly affect molecular shape and are always taken into account during simulations. We first review two widely used methods for deriving molecular conformations, the simple rotations scheme and the Denavit-Hartenberg local frames method. We discuss their disadvantages which include extensive bookkeeping, accumulation of numerical errors, and redundancies in the local frames used. Then we introduce a new, fast, and accurate method called the atomgroup local frames method. This new method not only eliminates the disadvantages of earlier approaches but also provides lazy evaluation of atom positions and reduces the computational cost. Our method is especially useful in applications where many conformations are generated or updated such as in energy minimization and conformational search.     

Physicochemical characterization of α‐chitin, β‐chitin,and γ‐chitin separated from natural resources

We isolated α‐chitin, β‐chitin, and γ‐chitin from natural resources by a chemical method to investigate the crystalline structure of chitin. Its characteristics were identified with Fourier transform infrared (FTIR) and solid‐state cross‐polarization/magic‐angle‐spinning (CP–MAS) ¹³C NMR spectrophotometers. The average molecular weights of α‐chitin, β‐chitin, and γ‐chitin, calculated with the relative viscosity, were about 701, 612, and 524 kDa, respectively. In the FTIR spectra, α‐chitin, β‐chitin, and γ‐chitin showed a doublet, a singlet, and a semidoublet at the amide I band, respectively. The solid‐state CP–MAS ¹³C NMR spectra revealed that α‐chitin was sharply resolved around 73 and 75 ppm and that β‐chitin had a singlet around 74 ppm. For γ‐chitin, two signals appeared around 73 and 75 ppm. From the X‐ray diffraction results, α‐chitin was observed to have four crystalline reflections at 9.6, 19.6, 21.1, and 23.7 by the crystalline structure. Also, β‐chitin was observed to have two crystalline reflections at 9.1 and 20.3 by the crystalline structure. γ‐Chitin, having an antiparallel and parallel structure, was similar in its X‐ray diffraction patterns to α‐chitin. The exothermic peaks of α‐chitin, β‐chitin, and γ‐chitin appeared at 330, 230, and 310, respectively. The thermal decomposition activation energies of α‐chitin, β‐chitin, and γ‐chitin, calculated by thermogravimetric analysis, were 60.56, 58.16, and 59.26 kJ mol^?1, respectively. With the Arrhenius law, ln β was plotted against the reciprocal of the maximum decomposition temperature as a straight line; there was a large slope for large activation energies and a small slope for small activation energies. α‐Chitin with high activation energies was very temperature‐sensitive; β‐Chitin with low activation energies was relatively temperature‐insensitive. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3423–3432, 2004     

A simple,fast and convenient new method for predicting the stability of nitro compounds

Journal of Computer-Aided Molecular Design - A new method has been proposed to understand and predict the stability of nitro compounds. This method uses the maximum electron densities at the...     

New Effective Synthetic Method for Preparation of N,N-Dichlorocarbamates

A rapid, efficient, economical, and easy-to-scale method for the effective conversion of carbamates to corresponding N,N-dichlorocarbamates by using sodium hypochlorite in acidic medium has been described. N,N-Dichlorocarbamates were obtained in quantitative yield through a simple workup in reduced reaction time.

A Clean,Mild, and Selective Oxidation of Sulfides to Sulfoxides Using NaClO/H2SO4 in Aqueous Media

A range of sulfides can be selectively oxidized to the corresponding sulfoxides in good yields using NaClO/H₂SO₄ in both water and 50:50 water:EtOH as solvent. Two new compounds are reported that show a diastereoselective oxidation in 2-phenylthioalcohols with possible neighboring hydroxyl group participation with a logic proposed mechanism.     

A new extraction method for the spectrophotometric determination of phosphates

The paper describes new procedures of extraction spectrophotometric determination of phosphates, based on the extraction of the ion associates of complex anions of 12-molybdatophosphoric acid, its “molybdenum blue,” and anion of 11-molybdatovanadatophosphoric acid with a cation of cationogenic tenside. The methods were applied to the determination of phosphorus in the samples of soil, plants, and water from lysimetric studies.     

金属分析用新型油样快速预处理方法的研究(蒸发-氧化法)

提出了一种新型快速油样预处理方法。方法基于蒸发-氧化原理,可在1．5～4h内将油样中的金属元素转化为氧化物粉末,与等离子体发射光谱（ICP-AES）、原子吸收光谱（AAS）等检测方法相结合,可实现油品中金属含量的快速测定。     

A method for constant-rate heating of milligram-sized samples

Heating a milligram-sized sample of material at a constant heating rate is usually achieved by controlling the temperature of an electric-resistance furnace with a proportional integral derivative (PID) controller. Here we present a new method for constant-rate heating that is based on a semi-empirical mathematical expression relating sample temperature, heating rate, and electric power supplied to the furnace. This method uses PID control only for second-order corrections of the heating rate. The linearity of the sample temperature vs. time curves obtained by applying this method to a simple furnace setup is the same as the linearity of the curves generated by modern commercial thermogravimetric analyzers.     

5-氯-2-硝基苯胺合成5-氯-苯并氧化呋咱反应的密度泛函研究

利用密度泛函理论(DFT)的B3LYP/6-31G(d,p)计算方法研究了次氯酸钠氧化环化5-氯-2-硝基苯胺合成5-氯-苯并氧化呋咱的反应, 采用连续介质模型(PCM)评估了溶剂效应. 提出两种可能的分步反应通道: (1)氧化、移氢、脱水和环化, (2)移氢、亚氨基氢扭转、氧化、脱水和环化|前者为优势通道. 非极性的CCl₄溶剂有较低的活化能垒, 比极性的乙醇溶剂更有利于5-氯-2-硝基苯胺的合成. 标题反应的机理类似于次氯酸钠氧化邻硝基苯胺合成苯并氧化呋咱, 但其速控步的活化能垒更低, 反应更易进行.     

邻溴苯胺/丙烯醛Schiff碱分子内Heck反应——合成喹啉的新方法

探讨了一种以邻溴苯胺和丙烯醛为原料合成喹啉的新方法,对反应条件进行了优化,并利用质谱和红外光谱分析确认了合成产物的结构.结果表明,以邻溴苯胺和丙烯醛为原料,经2步反应可得到喹啉:首先,邻溴苯胺和丙烯醛反应生成Schiff碱;随后,Schiff碱在催化剂和N2保护下经分子内Heck反应形成目标产物(总产率为45.1%).该合成方法具有操作简单、易于控制、催化剂可重复使用等优点.     

A new fast method for field screening of polychlorinated biphenyls in air

A new fast method for the detection of a sum parameter for polychlorinated biphenyls in air is presented. Air pollutants are sampled on a thermodesorbable silicone-coated glass fibre filter. Analysis is carried out by a mobile GC-MS system with short GC columns. Total time for analysis in the field is about 10 min. A novel data evaluation is used for quantification. To evaluate the GC run, signals of the characteristic ion traces of each degree of chlorination are integrated. Superposition of ion fragments in the low-resolution GC run are eleminated by a special algorithm.