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1.
The full characterization of chitin obtained from squid, shrimp, prawn, lobsters, and king crab is reported. Elemental analysis, including metals such as Ca, Mg, Zn, Cd, Hg, Cr, Mn, Cu, and Pb, was performed, which is quite relevant because the skeleton composition is slightly different for each species. The morphology was studied by means of TEM and their compositions were determined by energy‐dispersive X‐ray analysis. 13C cross polarization/magic angle spinning NMR was applied to determine the chemical shift of all the carbons and the difference between them. Chitin was isolated by using chemical methods, alternating hydrochloric acid and sodium hydroxide. The α‐chitin from shrimp, prawn, lobsters, and king crabs showed two signals at 73.7 and 75.6 ppm. Meanwhile, the β‐chitin from squid exhibited one signal at 75.2 ppm. FTIR studies were used to analyze α‐chitin from shrimp and β‐chitin from squid. The α‐chitin exhibited amide I vibration modes at 1660 and 1627 cm?1, whereas the β‐chitin showed one band at 1656 cm?1. X‐ray diffraction showed that α‐chitin is orthorhombic (a = 4.74 Å, b = 18.86 Å, and c = 10.32 Å) and β‐chitin had a monoclinic dihydrated form (a = 4.80 Å, b = 10.40 Å, c = 11.10 Å, and β = 97°). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1876–1885, 2004 相似文献
2.
《分离科学与技术》2012,47(11):2405-2418
Abstract Application of membrane technology to whey protein separation is an interesting development that has seen growth in recent years. In particular, modification of existing membranes to impart charge properties on the membrane surface or in the pores has been shown to improve membrane selectivity, product purity, and throughput of protein solutions. This paper focuses on exploring the effects of membrane charge and solution pH on filtration of the major whey proteins α‐lactalbumin (14.1 kDa) and β‐lactoglobulin (18.4 kDa) using functionalized PES membranes. The membranes have an open pore structure containing charged sulfonated grafted polymer chains that allows for greater protein retention. The modified membranes were synthesized by polymerization of styrene in the membrane pores followed by sulfuric acid treatment of the resulting polystyrene grafts. The charged membrane gave a calculated selectivity of five times better than the raw membrane at pH 7.2 based on data from single protein transmission experiments. The enhanced selectivity of the tailor‐made membrane was due to increased retention of β‐lactoglobulin due to a reduction in molecular sieving combined with electrostatic repulsion between negatively charged β‐lactoglobulin and the negatively charged membrane. 相似文献
3.
Dr. Valentina Palmieri Dr. Giuseppe Maulucci Dr. Alessando Maiorana Dr. Massimiliano Papi Prof. Marco De Spirito 《Chembiochem : a European journal of chemical biology》2013,14(17):2362-2370
The α‐crystallin family of small heat shock proteins possesses chaperone activity in response to stress and is involved in several neurological, muscular, and ophthalmic pathologies. This family includes the vertebrate lens protein α‐crystallin, associated with cataract disease. In this study, by combining small‐angle X‐ray and light scattering techniques, the structure and shape of α‐crystallin was revealed in its native state and after a transition caused by heat stress. Below critical temperature (Tc), α‐crystallin appears as an ellipsoid with a central cavity; whereas at high temperatures the cavity almost disappears, and the protein rearranges its structure, increasing the solvent‐exposed surface while retaining the ellipsoidal symmetry. Contextually, at Tc, α‐crystallin chaperone binding shows an abrupt increase. By modelling the chaperone activity as the formation of a complex composed of α‐crystallin and an aggregating substrate, it was demonstrated that the increase of α‐crystallin‐exposed surface is directly responsible for its gain in chaperone functionality. 相似文献
4.
Ho Lim Sunhee Woo Hong Sig Kim Seung‐Keun Jong Junsoo Lee 《European Journal of Lipid Science and Technology》2007,109(11):1124-1127
We evaluated the usefulness of saponification, direct solvent extraction, and Soxhlet extraction as extraction methods to determine the amounts of tocopherols in soybeans. Soxhlet extraction yielded the highest analytical values for each tocopherol homolog and was the best method for quantifying tocopherols in soybeans. Coupling of simple Soxhlet extraction with HPLC provided a highly reproducible procedure to quantify tocopherols in soybeans. The percent mean recovery ± standard deviation (n = 5) was 103.2 ± 1.21, 109.8 ± 4.18, 93.8 ± 1.12, and 106.9 ± 1.54% for α‐, β‐, γ‐, and δ‐tocopherol, respectively. The linearity test for quantification was carried out over the ranges of 0.4–10.0, 0.2–4.0, 2.0–16.0, and 0.4–10.0 µg/mL for α‐, β‐, γ‐, and δ‐tocopherol, respectively. Regression analysis showed an excellent linear relationship (R2 >0.998), and the results of the validation parameters were generally reliable and satisfactory. 相似文献
5.
Optimum production of extracellular, thermostable amylolytic enzymes (α and β‐amylase) by a newly isolated bacterium, Bacillus stearothermophilus, was investigated in a batch bioreactor. Starch and lactose at 1.0% and 3.0% (w/v) respectively were found to be optimum for maximum enzyme production. Optimization of cultural conditions (pH 7.0 and temperature 45°C) resulted in high bacterial specific growth rate (0.64 h?1), yielding 2.20 gL?1 biomass, 11.43 UmL?1 α‐amylase and 10.04 UmL?1 of β‐amylase. Hydrolysis of native starches from wheat, cassava, corn and potato at 60°C using the crude enzyme showed 60‐80% saccharification with potato starch showing the least and wheat starch showing the greatest hydrolysis. The Km and Vmax values of the crude α‐amylase for starch were 4.78 mg starch/mL and 6.67 mg/mL.min respectively. 相似文献
6.
Yohan Park Young Ju Lee Suckchang Hong Mi‐hyun Kim Myungmo Lee Taek‐Soo Kim Jae Kyun Lee Sang‐sup Jew Hyeung‐geun Park 《Advanced Synthesis \u0026amp; Catalysis》2011,353(18):3313-3318
A new enantioselective α‐alkylation of α‐tert‐butoxycarbonyllactams for the construction of β‐quaternary chiral pyrrolidine and piperidine core systems is reported. α‐Alkylations of N‐methyl‐α‐tert‐butoxycarbonylbutyrolactam and N‐diphenylmethyl‐α‐tert‐butoxycarbonylvalerolactam under phase‐transfer catalytic conditions (solid potassium hydroxide, toluene, −40 °C) in the presence of (S,S)‐3,4,5‐trifluorophenyl‐3,3′,5,5′‐tetrahydro‐2,6‐bis(3,4,5‐trifluorophenyl)‐4,4′‐spirobi[4H‐dinaphth[2,1‐c:1′,2′‐e]azepinium] bromide [(S,S)‐NAS Br] (5 mol%) afforded the corresponding α‐alkyl‐α‐tert‐butoxycarbonyllactams in very high chemical (up to 99%) and optical yields (up to 98% ee). Our new catalytic systems provide attractive synthetic methods for pyrrolidine‐ and piperidine‐based alkaloids and chiral intermediates with β‐quaternary carbon centers. 相似文献
7.
《分离科学与技术》2012,47(13):3039-3046
Abstract A macrocyclic vic‐dioxime (1) and its mononuclear Ni(II) complex (2) were studied as extractant. The aqueous solutions of Ag+, Mn2+, Pb2+, Ni2+, Cu2+, Cd2+, and Zn2+ picrates were used for extraction experiments. The solutions of the ligands in two different organic solvents were used as organic phases. The metal picrate extractions were carried out at 25±0.1°C by using UV‐visible spectrometry. The most effective transport was observed for Ag+ picrate among the tested metal picrates. The effect of pH on the extraction of Ag+ picrate was evaluated with the ligands. The ratio of extracted Ag‐complex to chloroform phase was 2:1 (L:M) for (2). In other cases the ratios were 1:1 for both (1) and (2). Molar ratio method was also used to demonstrate the composition. The values of the extraction constants (log Kex) were determined for the extracted Ag‐complexes. 相似文献
8.
Eugenia Karagiannidou Trond Rvik Strseth Hans‐Richard Sliwka Vassilia Partali Karl Egil Malterud Maria Tsimidou 《European Journal of Lipid Science and Technology》2003,105(8):419-426
Two modified carotenoids, β‐6‐hydroxy‐2, 5, 7, 8‐tetramethyl‐chromane carboxylic acid β‐apo‐8'‐carotenoate (Caro‐Trolox) and 3, 5‐di‐tert‐butyl‐4‐hydroxy benzoic acid β‐apo‐8'‐carotenoate (Caro‐BHT) were synthesized by esterification of β‐apo‐8'‐carotenol with Trolox and with 3, 5‐di‐tert‐butyl‐4‐hydroxy benzoic acid, respectively. Their activity under light exposure was examined comparatively to that of Trolox, α‐tocopherol, β‐carotene, β‐apo‐8'‐carotenoic acid (CA} and ethyl β‐apo‐8'‐carotenoate. The substrate used was purified sunflower oil. In the absence of a photosensitizer (240 W/m2 , 25 °C) Caro‐Trolox (200 mg/kg) behaved as an antioxidant and was quite stable (1/5 of the initial amount remained after 2‐wk storage). Caro‐BHT (200 mg/kg) showed no antioxidant activity and was quite unstable (it was destroyed within 7 d). In the presence of 5 mg/kg chlorophyll α (12000 lx, 25 °C) similar observations were made. The activity of Caro‐Trolox was concentration‐dependent. At a 100‐mg/kg level of addition its activity was similar to that of the mixture of α‐t_copherol (100 mg/kg) and β‐carotene (10 mg/kg). Its performance at the 10‐mg/kg level was slightly better than that of the other carotenoids. The antioxidant behavior of the modified carotenoids was attributed to the presence of the phenolic moiety as supported by the results of the 1, 1‐diphenyl‐2‐picrylhydrazyl test (e.g. EC50 after 15 min: 26.2, Caro‐Trolox; 35.8, Caro‐BHT; 122, CA; 22.3, Trolox). 相似文献
9.
David A. Fulton Anthony R. Pease J. Fraser Stoddart 《Israel journal of chemistry》2000,40(3-4):325-333
Per-6-amino-2,3-dimethyl-ß-cyclodextrin was prepared very efficiently as its hydrochloride salt from native ß-cyclodextrin in four steps and 89% overall yield. O-Acetyl-protected ß-D-thioglucose and ß-D-thiolactose derivatives, containing short spacer arms terminated with carboxylic acid functions, were prepared by the BF3·OEt2-catalyzed thioglycosylation of ß-D-glucose pentaacetate and ß-lactose octaacetate with 3-mercaptopropionic acid, respectively. Utilizing amide bond formation as the key step, these thio-ß-D-glucosyl and lactosyl derivatives were coupled to per-6-amino-2,3-dimethyl-ß-cyclodextrin to afford, after deprotection, perfunctionalized ß-cyclodextrin-based clusters containing seven thio-ß-D-glucosyl and seven ß-lactosyl appendages, respectively. Molecular modeling of both these ß-cyclodextrin-based clusters revealed the glucose and lactose clusters to be approximately 23 Å and 27 Å in diameter, respectively, and approximately 19 Å in height in both cases. The association constants for the complexation of the anti-inflammatory drug naproxen by ß-cyclodextrin, per-2,3-dimethyl-ß-cyclodextrin, and the lactose cluster of ß-cyclodextrin in 0.01 M phosphate buffered saline solution (pH 7.4) were found by UV-vis spectrophotometric titration to be 374 ± 75 M−1, 351 ± 70 M−1, and 165 ± 33 M−1, respectively. 相似文献
10.
E. Fischer M. Knippel K.-M. Wollin A. Klmn Gy. Argay 《Advanced Synthesis \u0026amp; Catalysis》1983,325(2):261-268
Stereochemical Investigations of Heterocyclic Compounds. XII. Structural Investigations of 1-(2-Amino-1-cyano-2-thio)ethene Pyridinium Ylides Two isomerization processes were found by 1H-d-n. m. r. characterized by ΔG* = 67 ± 4 KJ/mol for E- Z-isomerization and ΔG* = 46 ± 5 KJ/mol for the hindered rotation of the pyridine substituent in 1a . The structure of 1b was solved by direct method. Crystals are monoclinic space group P21/n, a = 13.682(3), b = 9.452(1), C = 19.713(6) Å, β = 96.42(2)°, V = 2533.3 Å3, Dx = 1.328 Mg · m−3, Z = 8. Both E- and Z-isomeres of 2b are found in the crystal lattice. The amino C distance with 1.369 (1,387) Å is shorter than the theoretical single bond distance. The formal CC double bond with 1.377 (1.391) Å is considerably longer than 1.337 Å observed in the some alkenes. 相似文献
11.
The copolymers of (Z)‐4‐oxo‐4‐phenoxyl‐2‐butenoic acid with styrene (PSt/OPBA) and their macromolecular luminous lanthanide complexes (Ln‐PSt/OPBA) have been synthesized and characterized by means of GPC, elemental analysis, FTIR, X‐ray powder diffraction, spectral analysis, and thermal analysis. The IR studies showed that the carboxylic groups on the side chain of the polymer were coordinated to lanthanide ions by bidentate manner. However, the ethereal oxygen, instead of carbonyl, also bonded to the central lanthanide ions, which was an intriguing phenomenon for ester‐coordinated complexes. X‐ray diffraction experiments revealed that these PSt/OPBA copolymers were amorphous, but Ln‐PSt/OPBA were crystalline, in which the complex Eu‐Lc belonged to a high symmetric structure of orthorhombic quadratic system, with a = 10.59 ± 0.02 Å, c = 8.02 ± 0.01 Å; c/a = 0.763. In addition, the value δ (the number of free carboxylic groups) in Ln‐PSt/OPBA complexes increased with the decreasing mole ratio of styrene in the copolymers, while it decreased with increasing pH values of the solution. Eu3+ and Tb3+ complexes exhibited characteristic fluorescence with comparatively high brightness and good monochromaticity, and the fluorescence intensity was enhanced with increasing the content of lanthanide up to around 18 wt % without typical fluorescence concentration quenching behavior in the solid state. So using polymers as a matrix, Ln‐PSt/OPBA are likely to provide new materials that possess specific properties and desired features. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
12.
The pH,temperature, and protein structure effect on β‐lactoglobulin A and B separation in anion‐exchange chromatography
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The effect of pH and temperature on separating a mixture of similar proteins, namely β‐lactoglobulin A (LGA) and β‐lactoglobulin B (LGB) in anion‐exchange chromatography is explored. The proteins carry a slight difference in negative charge at basic pH, providing a separation basis on an Q Sepharose Fast Flow anion‐exchange resin. They were separated at different temperatures and pH values, and the separation factor was evaluated. The experimental results were matched to a theoretical model to compute the equilibrium constant KA. The data shows that an increase in temperature and pH leads to an increase in the retention time of the proteins. The results were correlated with the net charge of the molecule for the separation so that the elution can be simulated for any condition that was studied. The tertiary structures of LGA and LGB are analyzed to illustrate the structure effect on the separation. © 2018 American Institute of Chemical Engineers AIChE J, 64: 1928–1937, 2018 相似文献
13.
Dr. Laurent David Dr. Mark Wenlock Dr. Patrick Barton Dr. Andreas Ritzén 《ChemMedChem》2021,16(17):2669-2685
Chameleonic properties, i. e., the capacity of a molecule to hide polarity in non-polar environments and expose it in water, help achieving sufficient permeability and solubility for drug molecules with high MW. We present models of experimental measures of polarity for a set of 24 FDA approved drugs (MW 405-1113) and one PROTAC (MW 1034). Conformational ensembles in aqueous and non-polar environments were generated using molecular dynamics. A linear regression model that predicts chromatographic apparent polarity (EPSA) with a mean unsigned error of 10 Å2 was derived based on separate terms for donor, acceptor, and total molecular SASA. A good correlation (R2=0.92) with an experimental measure of hydrogen bond donor potential, Δlog Poct-tol, was found for the mean hydrogen bond donor SASA of the conformational ensemble scaled with Abraham's A hydrogen bond acidity. Two quantitative measures of chameleonic behaviour, the chameleonic efficiency indices, are introduced. We envision that the methods presented herein will be useful to triage designed molecules and prioritize those with the best chance of achieving acceptable permeability and solubility. 相似文献
14.
Martin Studer Stefan Burkhardt Hans‐Ulrich Blaser 《Advanced Synthesis \u0026amp; Catalysis》2001,343(8):802-808
The hydrogenation of carboxylic acid derivatives at room temperature was investigated. With a mixed Rh/Pt oxide (Nishimura catalyst), low to medium activity was observed for various α‐amino and α‐hydroxy esters. At 100 bar hydrogen pressure and 10% catalysts loading, high yields of the desired amino alcohols and diols were obtained without racemization. The most suitable α‐substituents were NH2, NHR, and OH, whereas β‐NH2 were less effective. Usually, aromatic rings were also hydrogenated, but with the free bases of amino acids as substrates, some selectivity was observed. No reaction was found for α‐NR2, α‐OR, and unfunctionalized esters; acids and amides were also not reduced under these conditions. A working hypothesis for the mode of action of the catalyst is presented. 相似文献
15.
The nucleating ability of p‐cyclohexylamide carboxybenzene (β‐NA) towards isotactic polypropylene (iPP) was investigated by differential scanning calorimetry, X‐ray diffraction, polarized optical microscopy and scanning electron microscopy. β‐NA is identified to have dual nucleating ability for α‐iPP and β‐iPP under appropriate kinetic conditions. The formation of β‐iPP is dependent on the content of β‐NA. The content of β‐phase can reach as high as 96.96% with the addition of only 0.05 wt% β‐NA. Under non‐isothermal crystallization the content of β‐iPP increases with increasing cooling rate. The maximum β‐crystal content is obtained at a cooling rate of 40 °C min–1. The supermolecular structure of the β‐iPP is identified as a leaf‐like transcrystalline structure with an ordered lamellae arrangement perpendicular to the special surface of β‐NA. Under isothermal crystallization β‐crystals can be formed in the temperature range 80–140 °C. The content of β‐crystals reaches its maximum value at a crystallization temperature of 130 °C. © 2012 Society of Chemical Industry 相似文献
16.
《分离科学与技术》2012,47(4):835-845
Abstract Two new macrocyclic ligands, containing nitrogen and sulfur donor atoms were designed and synthesized in a multi‐step reaction sequence. The macrocycles with amide group were used in solvent extraction of picrates of metals such as Ag+, Hg2+, Cd2+, Zn2+, Cu2+, Ni2+, Mn2+, Co2+ and Pb2+ from aqueous phase to the organic phase. The metal picrate extractions were investigated at 25±0.1°C by using UV‐visible spectrometry. The extractability and selectivity of the mentioned metal picrates were evaluated according to the organic solvents. The values of the extraction constants (log Kex) and the complex compositions were determined for the extracted complexes. 相似文献
17.
《分离科学与技术》2012,47(14):3243-3257
Abstract Synthetic procedures for new mixed‐donor macrocycle compounds were reported. The macrocyclic compounds were used in solvent extraction metal picrates such as Ag+, Hg2+, Cd2+, Zn2+, Cu2+, Ni2+, Mn2+, Pb2+, and Co2+. The metal picrate extractions were investigated at 25±0.1°C with the aid of UV‐visible spectrometry. It was found that 6,7,9,10,12,13,23,24‐octahydro‐19H,26Hdibenzo[h,t](1,4,7,13,16,22,10,19) dioxatetrathiadiazasiclotetracosine‐20,27(21H,28H)‐dione showed selectivity towards Ag+, Hg2+, and Cd2+ among the other metals. The extraction constants (Log Kex) and complex compositions were determined for the Ag+ and Hg2+ complexes for this compound and 9,10,12,13,23,24,26,27,29,30‐decahydro‐5H,15H‐dibenzo‐[h,w][1,4,7,13,16,19,25‐,10,22] dioxapentathiadiazacycloheptacosine‐6,16(7H,17H)‐dione. 相似文献
18.
Shi‐Wei Wang Wei Yang Guan Gong Bang‐Hu Xie Zheng‐Ying Liu Ming‐Bo Yang 《应用聚合物科学杂志》2008,108(1):591-597
The effect of α‐ and β‐nucleating agents (NA) of various amounts on the fracture behavior of polypropylene‐co‐ethylene (CPP) was evaluated using the essential work of fracture (EWF) method. The specific EWF values of CPPs incorporated with α‐NA of different amount were all lower than that of pure CPP, while the specific nonessential work of fracture was the highest at relative low α‐NA loading (0.1 wt %), and then decreased with further increasing amount of α‐NA. Similar trend of variation was observed with increasing amount of β‐NA in CPP, and it was found that the variation of Kβ for β‐NA nucleated CPP versus NA content accorded well with the EWF versus NA content, which indicated that the addition of β‐NA could lead to effectively increased β‐crystal content and consequently improved fracture resistance of CPP. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
19.
Lithium aluminate (α‐/β‐LiAlO2) particles were fabricated using three methods. The first method used organic glycerin and triethylene glycol which functioned as a catalyst for fabrication of α‐LiAlO2 particles with Al(OH)3 and LiOH·H2O as the starting materials. As a result of the heat‐treatment of the starting materials, α‐/β‐LiAlO2 particles could be obtained. The amount of α‐LiAlO2 particles in α‐/β‐LiAlO2 increased slightly as more organics were added. Additionally, when synthesised α‐/β‐LiAlO2 particles were heat‐treated in a CO2 gas flow, β‐LiAlO2 was partially transformed to α‐LiAlO2. In the second method, molten salts (Li2/Na2/K2CO3) were used as a catalyst to fabricate α‐LiAlO2 as a major phase, however, this method requires a washing process which can produce unexpected impurities. In the third method, pure α‐LiAlO2 was obtained by heat‐treatment of cheap sources such as Li2CO3 and Al(OH)3 at 600–800 °C. The mean particle size (604 nm–11.85 μm) and the specific surface area (3.22–11.4 m2 g–1) of α‐LiAlO2 were suitable for reinforcing the matrix and tape casting. Lastly, this study examined the effect of CO2 for the synthesising of α‐LiAlO2 particles. 相似文献
20.
Influence of Sr2+ on Calcium‐Deficient Hydroxyapatite Formation Kinetics and Morphology in Partially Amorphized α‐TCP
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Katrin Hurle Juergen Neubauer Friedlinde Goetz‐Neunhoeffer 《Journal of the American Ceramic Society》2016,99(3):1055-1063
Hydration of partially amorphized α‐TCP powders with Sr2+ concentrations ranging from 0 to 10 mol% substitution for Ca2+ was analyzed by isothermal calorimetry and quantitative in‐situ XRD. Hydration of both crystalline α‐TCP and amorphous TCP (ATCP) forming CDHA was retarded to an increasing extent with increasing Sr2+ content. Sr2+ slightly reduced the crystallite size (XRD coherent scattering domains) of the CDHA formed during hydration, while the size of crystals visible under SEM was not noticeably affected. Reaction enthalpies of ΔHR(Sr‐α‐TCP→Sr‐CDHA) = 122 ± 8 J/gTCP and ΔHR(Sr‐ATCP→Sr‐CDHA) = 257 ± 8 J/gTCP were determined for the hydration of crystalline α‐TCP and ATCP containing 5 mol% Sr2+ substitution for Ca2+. This is comparable with the corresponding reaction enthalpies previously obtained for undoped samples, which are 106 ± 7 J/gTCP for α‐TCP and 250 ± 7 J/gTCP for ATCP. 相似文献