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Adrover M Esposito V Martorell G Pastore A Temussi PA 《Journal of the American Chemical Society》2010,132(45):16240-16246
All globular proteins undergo transitions from their native to unfolded states if exposed either to cold or to heat perturbation. While the heat-induced transition is well described for a large number of proteins, in media compatible with natural environments, the limited number of examples of cold denatured states concern proteins artificially destabilized, for instance, by the presence of denaturants, ad hoc point mutations, or both. Here, we provide a characterization of the low temperature unfolded state of Yfh1, a natural protein that undergoes cold denaturation around water freezing temperature, in the absence of any denaturant. By achieving nearly full assignment of the NMR spectrum, we show that at -1 °C, Yfh1 has all the features of an unfolded protein, although retaining some local, residual secondary structure. The effect is not uniform along the sequence and does not merely reflect the secondary structural features of the folded species. The N-terminus seems to be dynamically more flexible, although retaining some nascent helix character. Interestingly, this region is the one containing functionally important hot-spots. The β-sheet region and the C-terminal helix are completely unfolded, although experiencing some conformational exchange, partly due to the presence of several prolines. Ours is the first step toward a full characterization of the low temperature unfolded state of a natural protein, reached without the aid of any destabilizing agent. We discuss the implications of our findings for understanding cold denatured states. 相似文献
95.
Angela Chambery Antimo Di Maro Carmen Sanges Valeria Severino Maura Tarantino Annalisa Lamberti Augusto Parente Paolo Arcari 《Analytical and bioanalytical chemistry》2009,395(7):2281-2291
Diagnostic techniques applied to the field of cultural heritage represent a very important aspect of scientific investigation.
Recently, proteomic approaches based on mass spectrometry coupled with traditional spectroscopic methods have been used for
painting analysis, generating promising results for binder’s protein identification. In the present work, an improved procedure
based on LC-ESI/Q-q-TOF tandem mass spectrometry for the identification of protein binders has been developed for the molecular
characterization of samples from an early-twentieth-century mural painting from the St. Dimitar Cathedral in Vidin, Bulgaria.
The proteomic investigation has led to the identification of both egg white and egg yolk proteins, according to traditional
old recipes for tempera paintings. In addition, beyond the egg components, the presence of caseins was also revealed, thus
suggesting the use of milk as binding medium, fixative or stabilising agent. Furthermore, for the first time, the capability
to discriminate the milk origin on the basis of alpha casein proteotypic peptides is reported, that are diagnostic for a given
species, thus opening interesting perspectives in art and archaeological fields. 相似文献
96.
In this paper we introduce a discretization methodology for Maxwell equations based on Mimetic Finite Differences (MFD). Following the lines of the recent advances in MFD techniques (see Brezzi et al. (2007) [14] and the references therein) and using some of the results of Brezzi and Buffa (2007) [12], we propose mimetic discretizations for several formulations of electromagnetic problems both at low and high frequency in the time-harmonic regime. The numerical analysis for some of the proposed discretizations has already been developed, whereas for others the convergence study is an object of ongoing research. 相似文献
97.
Palumbo Piccionello A Guarcello A Buscemi S Vivona N Pace A 《The Journal of organic chemistry》2010,75(24):8724-8727
The reaction of various 1,2,4-oxadiazoles with an excess of hydrazine in DMF has been investigated. 3-Amino-1,2,4-triazoles are produced through a reductive ANRORC pathway consisting of the addition of hydrazine to the 1,2,4-oxadiazole followed by ring-opening, ring-closure, and final reduction of the 3-hydroxylamino-1,2,4-triazole intermediate. The general applicability of 1,2,4-oxadiazoles ANRORC reactivity is demonstrated also in the absence of C(5)-linked electron-withdrawing groups. 相似文献
98.
Lucia Ambrosio M. Carla Aragoni Dr. Massimiliano Arca Dr. Francesco A. Devillanova Prof. Michael B. Hursthouse Prof. Dr. Susanne L. Huth Dr. Francesco Isaia Prof. Vito Lippolis Prof. Dr. Annalisa Mancini Dr. Anna Pintus Dr. 《化学:亚洲杂志》2010,5(6):1395-1406
The tetrabutylammonium (TBA+) salts of square‐planar monoanionic gold complexes of the unsymmetrically substituted Ar,H‐edt2? 1,2‐dithiolene ligands (Ar,H‐edt2?=arylethylene‐1,2‐dithiolato; Ar=phenyl ( 1 ?), 2‐naphthyl ( 2 ?), and 1‐pyrenyl ( 3 ?)) were synthesized and characterized by spectroscopic and electrochemical methods and the corresponding neutral species ( 1 , 2 , and 3 , respectively) were obtained in CH2Cl2 solution at room temperature by diiodine oxidation. The single‐crystal X‐ray diffraction structural data collected for (TBA+)( 2 ?), supported by DFT theoretical calculations, are consistent with the ene‐1,2‐dithiolate form of the ligand and the AuIII oxidation state. All complexes feature intense near‐IR absorptions (at about 1.5 μm) in their neutral states and Vis‐emitting properties in the 400–550 nm range, the energy of which is controlled by the charge of the complex in the case of the 3 ?/ 3 couple. The spectroscopic and electrochemical features of 1 x? and 2 x? (x=0, 1), both in their cis and trans conformations, were investigated by means of DFT and time‐dependent (TD) DFT calculations. 相似文献
99.
Romani A Vignolini P Tanini A Pampaloni B Heimler D 《Natural product communications》2010,5(11):1775-1780
Isoflavones are polyphenolic compounds found mainly in legumes the benefits of which have been widely studied and attributed in particular to their phytoestrogenic activity. The aim of this study was to evaluate the quali-quantitative composition of food supplements based on soy isoflavones (Glycine max L.) and red clover (Trifolium pratense). Six commercial food supplements (five soy-based and one red clover-based) were analyzed by HPLC/DAD/MS. Genistein, daidzein, glycitein, biochanin A and formononetin derivatives (glycosides and acylglycosides) were identified in the analyzed samples. Also the antiradical activities (towards the DPPH* radical) and Fe2+ chelating abilities were compared. 相似文献
100.
In this paper, we prove Poincaré and Sobolev inequalities for differential forms in L~1(R~n). The singular integral estimates that it is possible to use for L~p, p 1, are replaced here with inequalities which go back to Bourgain and Brezis(2007). 相似文献