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Search Results: 1 - 10 of 1275 matches for " Mihaela Hillebrand "
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Bovine and Human Serum Albumin Interactions with 3-Carboxyphenoxathiin Studied by Fluorescence and Circular Dichroism Spectroscopy
Aurica Varlan,Mihaela Hillebrand
Molecules , 2010, DOI: 10.3390/molecules15063905
Abstract: The interactions of 3-carboxyphenoxathiin with Bovine Serum Albumin (BSA) and Human Serum Albumin (HSA) have been studied by fluorescence and circular dichroism spectroscopy. The binding of 3-carboxyphenoxathiin quenches the BSA and HSA fluorescence, revealing a 1:1 interaction with a binding constant of about 105 M-1. In addition, according to the synchronous fluorescence spectra of BSA and HSA in presence of 3-carboxyphenoxathiin, the tryptophan residues of the proteins are most perturbed by the binding process. Finally, the distance between the acceptor, 3-carboxyphenoxathiin, and the donor, BSA or HSA, was estimated on the basis of the F?rster resonance energy transfer (FRET). The fluorescence results are correlated with those obtained from the circular dichroism spectra, which reveal the change of the albumin conformation during the interaction process.
Sorana Ionescu,Mihaela Hillebrand
Analele Universitatii Bucuresti : Chimie , 2003,
Abstract: The experimental data on 4-acetyldiphenylsulfide (I) were previously explained byconsidering the possibility of twisted intramolecular charge transfer (TICT) excited stateformation. In the present paper solvent dependent semiempirical calculations were performed insolvents of different polarities. The ground and excited states potential energy surfaces werebuilt in terms of the torsion angle about the single bond joining the two aromatic fragments ofthe molecule, acting as D and A. The ground state has quasiplanar geometry, but in the excitedstates also the orthogonal conformation corresponds to a minimum, stabilised in methanol due tothe large charge separation between the D and A fragments. The possibility of forming TICTexcited states for I and the solvent polarity effect on the relative stability of the TICT state isdiscussed.
Theoretical prediction of the deactivation pathways in the coumarin class
Cristina Stoica,Sorana Ionescu,Mihaela Hillebrand
Analele Universitatii Bucuresti : Chimie , 2005,
Abstract: Semiempirical and ab initio calculations for coumarin and some 3-substitutedderivatives were performed, in order to get an insight on the n-π* or π-π* nature of the firstexcited state and on the possible nonradiative deactivation pathways. The results indicate thatboth HOMO and LUMO are π-type orbitals, while the n orbital has a lower energy (HOMO-2 ordeeper) and the nature of the first transition is π-π*. The sequence of states calculated at theoptimized geometry of the first excited singlet state indicates that substitution in position 3determines changes of energy in the triplet manifold, meaning a change in the intersystemcrossing (ISC) rate and thus the emission efficiency. The results correlate well with theexperimental data on the ΦP/ΦF ratio.
Cristina Oncioiu,Anca Nicolae,Mihaela Hillebrand
Analele Universitatii Bucuresti : Chimie , 2002,
Abstract: The properties of the excited state of 2-acetylthianthrene (emission maxima, quantum yields,natural lifetime) were investigated in several solvents by means of steady-state fluorescencespectroscopy. The experimental data pointed out a significant bathochromic shift of the emissionmaxima in polar solvents. Considering the dependence of F or ! Stokes on both the solventpolarity function (Lippert- Mataga model) and the ETN values, the increase in the dipole momentvalue upon excitation was estimated. The results can be rationalized in terms with a pronouncedintramolecular charge transfer character of the first excited state. MO calculations bysemiempirical and ab initio methods were performed to support the experimental data.
Spectroscopic Investigations of the Binding Interaction of a New Indanedione Derivative with Human and Bovine Serum Albumins
Dana Stan,Iulia Matei,Carmen Mihailescu,Mihaela Savin,Mihaela Matache,Mihaela Hillebrand,Ion Baciu
Molecules , 2009, DOI: 10.3390/molecules14041614
Abstract: Binding of a newly synthesized indanedione derivative, 2-(2-hydroxy-3-ethoxybenzylidene)-1,3-indanedione (HEBID), to human and bovine serum albumins (HSA and BSA), under simulated physiological conditions was monitored by fluorescence spectroscopy. The binding parameters (binding constants and number of binding sites) and quenching constants were determined according to literature models. The quenching mechanism was assigned to a F?rster non-radiative energy transfer due to the HEBID-SA complex formation. A slightly increased affinity of HEBID for HSA was found, while the number of binding sites is approximately one for both albumins. The molecular distance between donor (albumin) and acceptor (HEBID) and the energy transfer efficiency were estimated, in the view of F?rster’s theory. The effect of HEBID on the protein conformation was investigated using circular dichroism and synchronous fluorescence spectroscopies. The results revealed partial unfolding in the albumins upon interaction, as well as changes in the local polarity around the tryptophan residues
Aura Tintaru,O. Maior,Mihaela Hillebrand,Elena Volanschi
Analele Universitatii Bucuresti : Chimie , 2003,
Abstract: The heteroaromatic compounds containing fragments with different donor-acceptorproperties have large applications in many fields in which charge separation represents arequired property. The present work is constituted in a spectral and electrochemical study of thebenzoyl derivatives of the phenoxathiine and dibenzo-para-dioxin. The reduction behaviour ofthe compounds was investigated using the cyclic voltametry and ESR technics. The experimentalresults were in agreement with the MO calculations.
Reaction of 2,2-Diphenyl-1-picrylhydrazyl with HO?, O2?–, HO– ,and HOO– Radicals and Anions
Elena N. Hristeac,Miron T. Caproiu,Gabriela Pencu,Mihaela Hillebrand,Titus Constantinescu,Alexandru T. Balaban
International Journal of Molecular Sciences , 2006, DOI: 10.3390/i7050130
Abstract: Using electronic absorption spectra and thin layer chromatography, the reactionof 2,2-diphenyl-1-picrylhydrazyl (DPPH) with O2?–, HO?, HO–, and HOO– anions and freeradicals revealed the formation of the para-nitro- and para-hydroxy-derivatives of 2,2-diphenyl-1-picrylhydrazine (DPPH-H) and of DPPH fragmentation products(diphenylamine, tetraphenylhydrazine). The reaction of DPPH with the O2?– anion-radical(from KO2 in benzene solution at room temperature in the presence of 18-crown-6 ether) ispseudo-first-order during the first 25 minutes.
Superdense Coding with GHZ and Quantum Key Distribution with W in the ZX-calculus
Anne Hillebrand
Electronic Proceedings in Theoretical Computer Science , 2012, DOI: 10.4204/eptcs.95.10
Abstract: Quantum entanglement is a key resource in many quantum protocols, such as quantum teleportation and quantum cryptography. Yet entanglement makes protocols presented in Dirac notation difficult to verify. This is why Coecke and Duncan have introduced a diagrammatic language for quantum protocols, called the ZX-calculus. This diagrammatic notation is both intuitive and formally rigorous. It is a simple, graphical, high level language that emphasises the composition of systems and naturally captures the essentials of quantum mechanics. In the author's MSc thesis it has been shown for over 25 quantum protocols that the ZX-calculus provides a relatively easy and more intuitive presentation. Moreover, the author embarked on the task to apply categorical quantum mechanics on quantum security; earlier works did not touch anything but Bennett and Brassard's quantum key distribution protocol, BB84. Superdense coding with the Greenberger-Horne-Zeilinger state and quantum key distribution with the W-state are presented in the ZX-calculus in this paper.
Effects of Total Resources, Resource Ratios, and Species Richness on Algal Productivity and Evenness at Both Metacommunity and Local Scales
Lars Gamfeldt,Helmut Hillebrand
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0021972
Abstract: The study of the interrelationship between productivity and biodiversity is a major research field in ecology. Theory predicts that if essential resources are heterogeneously distributed across a metacommunity, single species may dominate productivity in individual metacommunity patches, but a mixture of species will maximize productivity across the whole metacommunity. It also predicts that a balanced supply of resources within local patches should favor species coexistence, whereas resource imbalance would favor the dominance of one species. We performed an experiment with five freshwater algal species to study the effects of total supply of resources, their ratios, and species richness on biovolume production and evenness at the scale of both local patches and metacommunities. Generally, algal biovolume increased, whereas algal resource use efficiency (RUE) and evenness decreased with increasing total supply of resources in mixed communities containing all five species. In contrast to predictions for biovolume production, the species mixtures did not outperform all monocultures at the scale of metacommunities. In other words, we observed no general transgressive overyielding. However, RUE was always higher in mixtures than predicted from monocultures, and analyses indicate that resource partitioning or facilitation in mixtures resulted in higher-than-expected productivity at high resource supply. Contrasting our predictions for the local scale, balanced supply of resources did not generally favor higher local evenness, however lowest evenness was confined to patches with the most imbalanced supply. Thus, our study provides mixed support for recent theoretical advancements to understand biodiversity-productivity relationships.
Efeito do EGB761 (Extrato de Ginkgo biloba) sobre a qualidade de vida em pacientes asmáticos moderados submetidos a tratamento de manuten??o
Hillebrand, M. D.;Oliveira, W. F.;
Revista Brasileira de Farmacognosia , 2004, DOI: 10.1590/S0102-695X2004000300010
Abstract: the search for efficient and alternative therapies for the asthma control is an important factor to the improvement of life quality in asthmatic patients. the effects of ginkgo biloba extract (ginkgo biloba l.) in the response of asthmatics to the maintenance treatment for persistent moderate asthma were studied in a blind, randomized, placebo-controlled clinical trial.
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