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691.
Mädler S Barylyuk K Boeri Erba E Nieckarz RJ Zenobi R 《Journal of the American Society for Mass Spectrometry》2012,23(2):213-224
Chemical cross-linking in combination with high-mass MALDI mass spectrometry allows for the rapid identification of interactions
and determination of the complex stoichiometry of noncovalent protein–protein interactions. As the molecular weight of these
complexes increases, the fraction of multiply charged species typically increases. In the case of homomeric complexes, signals
from multiply charged multimers overlap with singly charged subunits. Remarkably, spectra recorded in negative ion mode show
lower abundances of multiply charged species, lower background, higher reproducibility, and, thus, overall cleaner spectra
compared with positive ion mode spectra. In this work, a dedicated high-mass detector was applied for measuring high-mass
proteins (up to 200 kDa) by negative ion mode MALDI-MS. The influences of sample preparation and instrumental parameters were
carefully investigated. Relative signal integrals of multiply charged anions were relatively independent of any of the examined
parameters and could thus be approximated easily for the spectra of cross-linked complexes. For example, the fraction of doubly
charged anions signals overlapping with the signals of singly charged subunits could be more precisely estimated than in positive
ion mode. Sinapinic acid was found to be an excellent matrix for the analysis of proteins and cross-linked protein complexes
in both ion modes. Our results suggest that negative ion mode data of chemically cross-linked protein complexes are complementary
to positive ion mode data and can in some cases represent the solution phase situation better than positive ion mode. 相似文献
692.
Collini E Todescato F Ferrante C Bozio R Scholes GD 《Journal of the American Chemical Society》2012,134(24):10061-10070
The possibility to transfer energy between molecular excitons across a metal film up to 150 nm thick represents a very attractive solution to control and improve the performances of thin optoeletronic devices. This process involves the presence of coupled surface plasmon polaritons (SPPs) at the two dielectric-metal interfaces, capable of mediating the interactions between donor and acceptor, located on opposite sides of the metal film. In this Article, the photophysics and the dynamics of an efficient SPP-mediated energy transfer between a suitable dye and a conjugated polymer is characterized by means of steady-state and time-resolved photoluminescence techniques. The process is studied in model multilayer structures (donor/metal/acceptor) as well as in electrically pumped heterostructures (donor/metal cathode/acceptor/anode), to verify the effects of applied electric fields on the efficiency and the dynamics of SPP-mediated energy transfer. A striking enhancement of the overall luminescence was recorded in a particular range of applied bias, suggesting the presence of cooperative effects between optical and electrical stimulations. 相似文献
693.
Donatella Capitani Noemi Proietti Marco Gobbino Luigi Soroldoni Umberto Casellato Massimo Valentini Elisabetta Rosina 《Analytical and bioanalytical chemistry》2009,395(7):2245-2253
An integrated study of microclimate monitoring, IR thermography (IRT), gravimetric tests and portable unilateral nuclear magnetic
resonance (NMR) was applied in the framework of planning emergency intervention on a very deteriorated wall painting in San
Rocco church, Cornaredo (Milan, Italy). The IRT investigation supported by gravimetric tests showed that the worst damage,
due to water infiltration, was localized on the wall painting of the northern wall. Unilateral NMR, a new non-destructive
technique which measures the hydrogen signal of the moisture and that was applied directly to the wall, allowed a detailed
map of the distribution of the moisture in the plaster underlying the wall panting to be obtained. With a proper calibration
of the integral of the recorded signal with suitable specimens, each area of the map corresponded to an accurate amount of
moisture. IRT, gravimetric tests and unilateral NMR applied to investigate the northern wall painting showed the presence
of two wet areas separated by a dry area. The moisture found in the lower area was ascribed to the occurrence of rising damp
at the bottom of the wall due to the slope of the garden soil towards the northern exterior. The moisture found in the upper
area was ascribed to condensation phenomena associated with the presence of a considerable amount of soluble, hygroscopic
salts. In the framework of this integrated study, IRT investigation and gravimetric methods validated portable unilateral
NMR as a new analytical tool for measuring in situ and without any sampling of the distribution and amount of moisture in
wall paintings. 相似文献
694.
Joanna Anastassopoulou Evridiki Boukaki Carla Conti Paolo Ferraris Elisabetta Giorgini Corrado Rubini Simona Sabbatini Teo Theophanides Giorgio Tosi 《Vibrational Spectroscopy》2009,51(2):270-275
Microimaging Fourier transform infrared spectroscopy is able to monitor differentiation between normal and malignant tissues. All the specimens, previously submitted to histological analysis, displayed abnormal spectra compared with the corresponding normal tissues with changes in many diagnostic bands like those arising from phosphate, C–O and CH stretching vibrational modes. The comparison between cancer (K) and connective (C) spectra evidenced the following differences: in the vCH region 3000–2800 cm−1 no hypomethylation effect was evident in K; the convolution of the bands of connective indicated an expected higher membrane fluidity; in the neoplastic zone, Amide I and II modes showed convoluted bands with maxima at 1651 and 1547 cm−1, respectively, indicating an α-helix conformation of proteins due to changes in the secondary structure proteins upon carcinogenesis. Other signature bands, such as the deformation O–P–O phosphate band at 965 cm−1, suggested DNA conformational changes in solid cancer, infiltrating cancer and neoplasia in the region 1350–800 cm−1. These characteristic bands have been monitored as a function of the degree of cancer progression. Chemometric methods, such as principal component analysis (PCA) and hierarchical clustering analysis (HCA) have been used in order to distinguish spectra of neoplastic and normal zones. 相似文献
695.
Luigi Angiolini Daniele Caretti Elisabetta Salatelli Monique Biesemans 《Journal of organometallic chemistry》2006,691(13):3043-3052
Three new resins are synthesized by radical co-polymerization of triorganotin-4-vinylbenzoates (substituent at tin = Me, Bu or Ph) with styrene and 1,4-divinylbenzene. The products prepared have been characterized by FT-IR and NMR spectroscopy both in the solid state and as swollen samples, showing a predominantly tetracoordinated tin atom. The catalytic activity of the above resins in a transesterification reaction has been tested using ethyl acetate and primary, secondary or tertiary alcohol, showing good results with the former, but not with the latter ones. Focussing on the different triorganotin substituents, a comparison between the prepared resins and low molecular weight analogues evidences a lower activity of the resins, due to their inhomogeneous operating conditions. However, the triphenyltin functionalized resin shows a transesterification activity comparable to the corresponding model compound. The reaction mechanism and the effects of Lewis acidity of the different groups linked to tin have been investigated by 1H and 119Sn hr-MAS NMR. 相似文献
696.
697.
Marta De Zotti Dr. Francesca Damato Fernando Formaggio Prof. Marco Crisma Dr. Elisabetta Schievano Dr. Stefano Mammi Prof. Bernard Kaptein Dr. Quirinus B. Broxterman Dr. Peter J. Felock Dr. Daria J. Hazuda Dr. Sheo B. Singh Dr. Jochen Kirschbaum Dr. Hans Brückner Prof. Claudio Toniolo Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(1):316-327
Integramide A is a 16‐amino acid peptide inhibitor of the enzyme HIV‐1 integrase. We have recently reported that the absolute stereochemistries of the dipeptide sequence near the C terminus are L ‐Iva14‐D ‐Iva15. Herein, we describe the syntheses of the natural compound and its D ‐Iva14‐L ‐Iva15 diastereomer, and the results of their chromatographic/mass spectrometric analyses. We present the conformational analysis of the two compounds and some of their synthetic intermediates of different main‐chain length in the crystal state (by X‐ray diffraction) and in solvents of different polarities (using circular dichroism, FTIR absorption, and 2D NMR techniques). These data shed light on the mechanism of inhibition of HIV‐1 integrase, which is an important target for anti‐HIV therapy. 相似文献
698.
699.
700.
Activation of Hsp90 Enzymatic Activity and Conformational Dynamics through Rationally Designed Allosteric Ligands 下载免费PDF全文
Dr. Sara Sattin Dr. Jiahui Tao Dr. Gerolamo Vettoretti Dr. Elisabetta Moroni Dr. Marzia Pennati Dr. Alessia Lopergolo Dr. Laura Morelli Dr. Antonella Bugatti Dr. Abbey Zuehlke Dr. Mike Moses Dr. Thomas Prince Dr. Toshiki Kijima Dr. Kristin Beebe Dr. Marco Rusnati Dr. Len Neckers Dr. Nadia Zaffaroni Prof. David A. Agard Prof. Anna Bernardi Dr. Giorgio Colombo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(39):13598-13608
Hsp90 is a molecular chaperone of pivotal importance for multiple cell pathways. ATP‐regulated internal dynamics are critical for its function and current pharmacological approaches block the chaperone with ATP‐competitive inhibitors. Herein, a general approach to perturb Hsp90 through design of new allosteric ligands aimed at modulating its functional dynamics is proposed. Based on the characterization of a first set of 2‐phenylbenzofurans showing stimulatory effects on Hsp90 ATPase and conformational dynamics, new ligands were developed that activate Hsp90 by targeting an allosteric site, located 65 Å from the active site. Specifically, analysis of protein responses to first‐generation activators was exploited to guide the design of novel derivatives with improved ability to stimulate ATP hydrolysis. The molecules’ effects on Hsp90 enzymatic, conformational, co‐chaperone and client‐binding properties were characterized through biochemical, biophysical and cellular approaches. These designed probes act as allosteric activators of the chaperone and affect the viability of cancer cell lines for which proper functioning of Hsp90 is necessary. 相似文献