86,626 research outputs found
Porcine odorant-binding protein: structural stability and ligand affinities measured by Fourier-transform infrared spectroscopy and fluorescence spectroscopy
No full textInfrared spectra show that the binding of the odorants 2-isobuthyl-3-mrthoxypyrazine (PYR) and 3,7-dimethyl-1-octanol (DMO) stabilises the tertiary structure of porcine OBP-I against thermal denaturation. The fluorescence emission spectrum of the single tryptophan shows a lambda(max) at 337 nm, indicating that the residue is not directly exposed to the solvent. Tryptophan does not appear to be involved in the odorant binding process and it is not accessible to the fluorescence quenchers NaI, CsCl and acrylamide. The binding of the fluorescent dye 1-aminoanthracene (1-AMA), a strong ligand, does not modify the tryptophan fluorescence spectrum. In contrast, the lambda(max) of 1-AMA bound to OBP-I is shifted from 537 to 481 nm, with a lambda(max) intensity increase by a factor of 80. Bound 1-AMA is displaced by odorant molecules in competitive binding assays and can be employed in simple and rapid binding assay, avoiding the use of radioactive ligands. The Scatchard plot shows that 1-AMA binds to OBP-I with a dissociation constant of 1.3 mu M and an equimolar stoichiometry. (C) 1999 Elsevier Science B.V. All rights reserved. RI Tanfani, Fabio/F-1441-201
Thymoquinone, a potential therapeutic agent of Nigella sativa, binds to site I of human serum albumin.
No full textThymoquinone, a potential therapeutic agent of Nigella sativa, binds to site I of human serum albumin
G. Lupidi a, 1, A. Scire b, 1, E. Camaioni c, K.H. Khalife a, G. De Sanctis a, F. Tanfani b, E. Damiani b, ,
a Dipartimento di Biologia M.C.A., Università degli Studi di Camerino, Camerino, Italy
b Dipartimento di Biochimica, Biologia e Genetica, Università Politecnica delle Marche, Ancona, Italy
c Dipartimento di Chimica e Tecnologia del Farmaco, Università degli Studi di Perugia, Perugia, Italy
Abstract
Thymoquinone (TQ) is the main constituent of Nigella sativa essential oil which shows promising in vitro and in vivo antineoplastic growth inhibition against various tumor cell lines. Because of the increasing interest to test it in pre-clinical and clinical researches for assessing its health benefits, we here evaluate the interactions between TQ and human serum albumin (HSA), a possible carrier of this drug in vivo. Binding to HSA was studied using different spectroscopic techniques. Fourier transform infrared (FT-IR) and circular dichroism (CD) spectroscopies suggest that the association between TQ and HSA does not affect the secondary structure of HSA. Using fluorescence spectroscopy, one mole of TQ was found to bind one mole of HSA with a binding constant of 2.39 ± 0.2 104 M−1. At 25 °C (pH 7.4), van’t Hoff’s enthalpy and entropy that accompany the binding were found to be −10.24 kJ/mol−1 and 45 J/mol−1 K−1 respectively. The thermodynamic analysis of the TQ-HSA complex formation shows that the binding process is enthalpy driven and spontaneous, and that hydrophobic interactions are the predominant intermolecular forces stabilizing the complex. Furthermore, displacement experiments using warfarin and ibuprofen indicate that TQ could bind to site I of HSA, which is also in agreement with the results of the molecular modeling study
Magnetic resonance imaging in childhood and adolescence with migraine and epilepsy: a case controlled study.
No full textA spectroscopic study on secondary structure and thermal unfolding of the plant toxin gelonin confirms some typical structural characteristics and unravels the sequence of thermal unfolding events
No full textGelonin from the Indian plant Gelonium multiflorum belongs to the type I ribosome-inactivating proteins (RIPs). Like other members of RIPs, this toxin glycoprotein inhibits protein synthesis of eukaryotic cells; hence, it is largely used in the construction of immunotoxins composed of cell-targeted antibodies. Lysosomal degradation is one of the main issues in targeted tumor therapies, especially for type I RIP-based toxins, as they lack the translocation domains. The result is an attenuated cytosolic delivery and a decrease of the antitumor efficacy of these plant-derived toxins; therefore, strategies to permit their release from endosomal vesicles or modifications of the toxins to make them resistant to degradation are necessary to improve their efficacy. Using infrared spectroscopy, we thoroughly analyzed both the secondary structure and the thermal unfolding of gelonin. Moreover, by the combination of two-dimensional correlation spectroscopy and phase diagram method, it was possible to deduce the sequence of events during the unfolding, confirming the typical characteristic of the RIP members to denature in two steps, as a sequential loss of tertiary and secondary structure was detected at 58 °C and at 65 °C, respectively. Additionally, some discrepancies in the unfolding process between gelonin and saporin-S6, another type I RIP protein, were detected
Effects of Fe(III) binding to the nucleotide-independent site of F1ATPase: enzyme thermostability and response to activating anions
No full textAbstractMitochondrial F1-ATPase was induced in different conformations by binding of specific ligands, such as nucleotides. Then, Fourier transform infrared spectroscopy (FT-IR) and kinetic analyses were run to evaluate the structural and functional effects of Fe(III) binding to the nucleotide-independent site. Binding of one equivalent of Fe(III) induced a localised stabilising effect on the F1-ATPase structure destabilised by a high concentration of NaCl, through rearrangements of the ionic network essential for the maintenance of enzyme tertiary and/or quaternary structure. Concomitantly, a lower response of ATPase activity to activating anions was observed. Both FT-IR and kinetic data were in accordance with the hypothesis of the Fe(III) site location near one of the catalytic sites, i.e. at the α/β subunit interface
A 3D-BPP approach for optimising stowage plans and terminal productivity.
No full textThis paper addresses the problem of determining stowage plans for containers in a ship, that is the so-called master bay plan problem (MBPP). MBPP is NP-complete [Botter, R.C., Brinati, M.A., 1992. Stowage container planning: A model for getting an optimal solution. IFIP Transactions B (Applications in Technology) B-5, 217–229; Avriel, M., Penn, M., Shpirer, N., 2000. Container ship stowage problem: Complexity and connection to the colouring of circle graphs. Discrete Applied Mathematics 103, 271–279]. We present a heuristic method for solving MBPP based on its relation with the three-dimensional bin packing problem (3D-BPP), where items are containers and the only bin is the ship. We look for stowage plans that take into a
proper account structural and operational constraints, related to both the containers and the ship, and maximise some important terminal performance indexes, such as the effective and mean net crane productivity.
Our aim is to evaluate how stowage plans can influence the performance of the quay. A validation of the proposed pproach with some test cases related to containership docks at the port of Genoa (Italy) is given. The results of real instances of the problem and the comparison with a validated heuristic for MBPP, show the effectiveness of the proposed approach in producing stowage plans that minimise the total loading time and allow an efficient use of the quay equipment
Effect of inhibitor binding to beta-subunits of F1ATPase on enzyme thermostability: A FT-IR spectroscopic analysis.
No full textEffect of neutral and acidic phospholipids on mitochondrial ATP synthase secondary structure
No full textThe secondary structure of delipidated and egg phosphatidylcholine or asolectin reconstituted mitochondrial ATP synthase complex from beef heart was investigated by Fourier transform infrared spectroscopy. Upon reconstitution, the infrared spectra of ATP synthase revealed an increase in turns and a concomitant decrease in beta-sheet content which occurred to a larger extent in the presence of asolectin rather than in the presence of egg phosphatidylcholine. These data correlate with kinetic data showing a higher ATPase activity of the asolectin reconstituted enzyme protein than the egg phosphatidylcholine reconstituted or delipidated enzyme complexes
Effect of inhibitor binding to beta subunits of F1 ATPase on enzyme thermostability: an FT-IR spectroscopic analysis.
No full textFT-IR analysis shows that treatment of F1ATPase with the inhibitors DCCD and Nbf-Cl, in the presence of saturating concentrations of ADP and AMP-PNP and in the absence of Mg2+, does not modify the secondary structure of the enzyme, but significantly modifies its compactness and thermal stability, although to different extents. Nbf-Cl causes a significant increase in stabilisation, in addition to that induced by nucleotides, while DCCD is less effective in this regard. Determination by HPLC of the exchange rate, in the absence of Mg2+, of tightly bound nucleotides of F1ATPase treated with the two inhibitors shows that DCCD does not significantly affect the exchange rate of ADP with AMP-PNP and vice versa in catalytic and non-catalytic tight sites, while Nbf-Cl selectively reduces the enzyme's capacity to exchange ADP bound in the tight catalytic site. It is suggested that the effects of DCCD, unlike those of Nbf-Cl, are closely related to the presence or absence of Mg2+
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