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71.
72.
This paper presents a new simple and sensitive method for the micro-determination of protein containing SH– and –S–S– groups based on the single sweep polarographic wave of an electroactive derivative. In 0.04molL–1 Na3PO4 and 0.2% ascorbic acid solution, protein is heated in a boiling water bath for 15min, the reaction product giving a sensitive reduction wave at –0.70V (vs. SCE). The wave height is linearly proportional to the concentration of protein. The calibration curves of bovine serum albumin (BSA), human serum albumin (HSA), ovalbumin (OVA) and lysozyme (Lyso) are constructed under the optimal conditions. For BSA and HSA, the linear ranges and detection limits are 0.05–24mgL–1 and 0.02mgL–1, respectively. The method has been applied to the determination of protein in human serum samples with satisfactory results. The mechanism of the polarographic wave was also studied, and the results show that S2– ion is released from the protein molecule during the derivatization reaction, the wave being attributed to the reduction of HgS. 相似文献
73.
Structure control within poly(amidoamine) dendrimers: size, shape and regio-chemical mimicry of globular proteins 总被引:1,自引:0,他引:1
This work describes the syntheses of a new poly(amidoamine) (PAMAM) dendrimer family possessing a disulfide function (cystamine) in its core. Traditional redox-chemistry associated with the disulfide core in these dendrimer structures, provides a versatile strategy for designing unique sizes, shapes and controlling the regio-disposition of chemical groups on the surface of these dendrimers. Various single site, sulfhydryl functionalized dendron reactants may be generated in situ, under standard reducing conditions (i.e. dithiothreitol (DTT)). Facile control of size, shape and chemical functionality placement involves covalent hybridization of these single point, sulfhydryl reactive dendron components. This is accomplished by re-oxidation in the presence of air, to yield generation/surface chemistry differentiated cross-over products which may be isolated by preparative thin layer or column chromatography. Differentiated cystamine core dendrimers derived from combination and permutation of lower generation (i.e. Gen.=0-3) sulfhydryl functionalized dendrons possessing amino, hydroxyl, acetamido or dansyl surface groups, were synthesized and isolated. They were characterized by a variety of methods including; 13C NMR, capillary electrophoresis (CE), gel electrophoresis (PAGE), thin layer chromatography (TLC) and electrospray (ES) or matrix assisted laser desorption ionization (MALDI-TOF) mass spectrometry. This general strategy has broad implications for the systematic size, shape and regio-chemical control of a wide range of dendritic nanostructures, many of which may be designed to mimic the sizes, shapes and regio specific chemo-domains observed for globular proteins. 相似文献
74.
Shyh-Horng Chiou 《中国化学会会志》1989,36(5):435-442
A rapid peptide-bond hydrolysis by means of microwave irradiation is introduced for the facile preparation of protein hydrolysates used for amino acid analysis. The optimal hydrolysis condition has been determined using several enzymes with known amino acid compositions. The effects of hydrolysis time on the recovery of various labile and hydrophobic amino acids are also exemplified in the microwave heating of standard amino acids. The method has been applied to the complete amino acid analysis with a single nonvolatile solvent of methanesulfonic acid with good recovery of tryptophan and half-cystine. It provides a radical expedition of protein and peptide hydrolysis via commercial microwave ovens and specially-designed Teflon-Pyrex tubes, circumventing the tedious procedures using vacuum-sealed pyrex lubes heating at 110°C for more than 24 h. This novel type of microwave chemistry associated with rapid peptide-bond cleavage is of great potential in the automation of the complete process of amino acid analysis starting from the preparation of protein hydrolysates. 相似文献
75.
Heat divided by ligand concentration vs. heat, similar to the Scatchard plot, was introduced to obtain the equilibrium constant
(K) and the enthalpy of binding (DH) using isothermal titration calorimetry data. Values of K and DH obtained by this linear
pseudo-Scatchard plot for a system with a set of independent binding sites (such as binding fluoride ions on urease and monosaccharide
methyl a-D-mannopyranoside on concavalin A) were remarkably like that obtained from a normal fitting Wiseman method and other
our technical methods. On applying this graphical method to study the binding of copper ion on myelin basic protein (MBP),
a concave downward curve obtained was consistent with the positive cooperativity in the binding. A graphical fitting by simple
method for determination of thermodynamic parameters was also introduced. This method is general, without any assumption and
restriction made in previous method. This general method was applied to the product inhibition study of adenosine deaminase.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
76.
Beate Hager Bettina Schwarzinger Heinz Falk 《Monatshefte für Chemie / Chemical Monthly》2006,137(2):163-168
Summary. Two model compounds for the green fluorescent protein chromophore were prepared. One of them incorporates the natural 4-hydroxybenzylidene
group of the natural tyrosin derived chromophore, the other one bears a methyl group instead of the hydroxy group. Whereas
the photochemically prepared (E)-diastereomer of the first compound very effectively reverted thermally (room temperature) to the thermodynamically stable
(Z)-diastereomer, the (E)-diastereomer of the second derivative proved to be stable even at elevated temperatures for more than a day. This finding
can be rationalized by constructing the appropriate resonance structures showing that only in the first case an effective
delocalization enables partial single bond character of the benzylidene double bond. From the standpoint of chemical etiology,
only Nature’s choice of the tyrosin derived chromophore of the green fluorescent protein provides an efficient radiationless
thermal relaxation channel for the unwanted photo-diastereomerization product formed after excitation besides the dominating
fluorescence channel of its chromophore. 相似文献
77.
Cartoni C Schininà ME Maras B Nonno R Vaccari G Di Baria MA Conte M Liu QG Lu M Cardone F Windl O Pocchiari M Agrimi U 《Journal of chromatography. A》2005,1081(1):122-126
Cerebral formation of the pathological isoform of the prion protein (PrP) is a crucial molecular event in prion diseases. The bank vole (Clethrionomys glareolus) is a rodent species highly susceptible to natural scrapie. The PrP gene of bank vole is polymorphic (Met/Ile) at codon 109. Here we show that homozygous 109Met/Met voles have incubation times shorter than heterozygous 109Met/Ile voles after experimental challenge with three different scrapie isolates. An HPLC-MS/MS method was optimized and applied to investigate whether in heterozygous animals both PrP allotypes are able to undergo pathological conversion. The results demonstrate that both allotypes of the prion protein participate to pathological deposition. 相似文献
78.
Boris Pejin Kristina Tešanović Dragica Jakovljević Sonja Kaišarević Filip Šibul Milena Rašeta 《Natural product research》2019,33(5):750-754
The polysaccharide (PSH) extracts from the edible mushroom species Coprinus comatus and Coprinellus truncorum were screened in liquid for their acetylcholinesterase inhibitory (AChE) activity. Both extracts were found to display inhibition of the aforementioned enzyme reaching similar IC50 values of 0.62 ± 0.07 and 0.61 ± 0.03 mg/mL, respectively. According to the means of FTIR spectroscopy, these PSH extracts mostly contained β-glucans. However, the presence of some proteins and polyphenolics as minor ingredients were also detected. Compared with existing literature data for anti-AChE activity of the sugar samples, the findings within this study may be treated as a profound bioactivity. Consequently, this study puts some light on the possible use of the screened macrofungi in the palliative treatment of Alzheimer’s disease. 相似文献
79.
Hermida-Ramón JM Brdarski S Karlström G Berg U 《Journal of computational chemistry》2003,24(2):161-176
An intramolecular NEMO potential is presented for the N-formylglycinamide molecule together with an intermolecular potential for the N-formylglycinamide-water system. The intramolecular N-formylglycinamide potential can be used as a building block for the backbone of polypeptides and proteins. Two intramolecular minima have been obtained. One, denoted as C5, is stabilized by a hydrogen bonded five member ring, and the other, denoted as C7, corresponds to a seven membered ring. The interaction between one water molecule and the N-formylglycinamide system is also studied and compared with Hartree-Fock SCF calculations and with the results obtained for some of the more commonly used force fields. The agreement between the NEMO and SCF energies for the complexes is in general superior to that of the other force fields. In the C7 region the surfaces obtained from the intramolecular part of the commonly used force fields are too flat compared to the NEMO potential and the ab initio calculations. We further analyze the possibility of using a charge distribution obtained from one conformation to describe the charge distribution of other conformations. We have found that the use of polarizabilities and generic dipoles can model most of the changes in charge density due to the different geometry of the new conformations, but that one can expect additional errors in the interaction energies that are of the order of 1 kcal/mol. 相似文献
80.
《Chemphyschem》2003,4(4):359-365
We studied the thermodynamic stability of a small monomeric protein, staphylococcal nuclease (Snase), as a function of both temperature and pressure, and expressed it as a 3D free‐energy surface on the p,T‐plane using a second‐order Taylor expansion of the Gibbs free‐energy change ΔG upon unfolding. We took advantage of a series of different techniques (small‐angle Xray scattering, Fourier‐transform infrared spectroscopy, differential thermal analysis, pressure perturbation calorimetry and densitometry) in the evaluation of the conformation of the protein and in evaluating the changes in the thermodynamic parameters upon unfolding, such as the heat capacity, enthalpy, entropy, volume, isothermal compressibility and expansivity. The calculated results of the free‐energy landscape of the protein are in good agreement with experimental data of the p,T‐stability diagram of the protein over a temperature range from 200 to 400 K and at pressures from ambient pressure to 4000 bar. The results demonstrate that combined temperature–pressure‐dependent studies can help delineate the free‐energy landscape of proteins and hence help elucidate which features and thermodynamic parameters are essential in determining the stability of the native conformational state of proteins. The approach presented may also be used for studying other systems with so‐called re‐entrant or Tamman loop‐shaped phase diagrams. 相似文献