Search results for "molécule"
showing 10 items of 19 documents
III. Biochemistry of S-layers
1997
During evolution prokaryotes have developed different envelope structures exterior to the cell wall proper. Among these surface components are regularly arranged S-layers and capsules. The structural characterization and the detailed chemical analysis of these surface molecules is a prerequisite to understand their biosynthesis and functional role(s) at the molecular level. Of particular interest are the glycosylated S-layer proteins which belong to the first prokaryotic glycoproteins ever described. Their characterization was performed on strains belonging to the thermophilic Bacillaceae and included structural studies and experiments to learn about the pathways for the glycan biosynthesis…
Design and computer simulations of 2D MeX2 solid-state nanopores for DNA and protein detection analysis
2020
Solid-state nanopores (SSN) have emerged as versatile devices for biomolecule analysis. One of the most promising applications of SSN is DNA and protein sequencing, at a low cost and faster than the current standard methods. SSN sequencing is based on the measurement of ionic current variations when a biomolecule embedded in electrolyte is driven through a nanopore under an applied electric potential. As a biomolecule translocates through the nanopore, it occupies the pore volume and blocks the passage of ions. Hence, ultrafast monitoring of ionic flow during the passage of a biomolecule yields information about its structure and chemical properties. The size of the sensing region in SSN is…
Vers le contrôle de l'alignement et de l'orientation : théorie et expérience
2010
This thesis is about the control and characterisation of the alignment and orientation of molecules by ultra short laser pulses on a theoretical and experimental approach. Alignment corresponds to a symmetric angular distribution of the molecular axis peaked along the laser field axis, whereas orientation provides an asymmetric distribution favouring one spatial direction. Orientation by sudden two-colour (2+1) pulses is studied extensively for the non resonant case and conditions required for achieving significant orientation are explored. A second two-colour scheme, where the second harmonic is in quasi resonance with a vibrational level of the molecule, is also presented and discussed. T…
Synthèses optimisées et caractérisations avancées de nanotubes de titanate et de leurs fonctionnalisations : vers l'élaboration de nanovecteurs de mo…
2017
The aim of this PhD thesis is to develop new nanohybrids based on titanate nanotubes (TiONts) in order to use them as nanocarrier of a therapeutic molecule: a stilbene phenol, 4'-hydroxy-4-(3-aminopropoxy)-trans-stilbene (HAPtS), which is a transresveratrol derivative.TiONts are synthesized by a hydrothermal treatment from a precursor of rutile titanium dioxide. Two methods of hydrothermal synthesis have been studied (the static and dynamic ones): the second approach uses an original hydrothermal device which provides a vigorous mechanical stirring during the hydrothermal process with controllable stirring time par hour. A parametric study was carried out to evaluate the effect of reaction …
Dynamique induite par champ laser femtoseconde intense : alignement moléculaire en milieu gazeux dense et effet Kerr
2011
This thesis is devoted to the study of dynamics induced by intense femtoseconds lasers pulses. The first studied dynamics deals with molecular alignment of CO2-X mixtures (X=CO2, Ar, N2), in dense gases (up to 20 bar). Up to now, this regime has never been studied experimentally. In the field-free regime (after laser/matter interaction), molecular alignment exhibits two components : a permanent alignment and a transient one. The influence of collisions appears through population transfers between rotational states, which leads to a decrease of these two contributions. Permanent alignment relaxation time is only tied to inelastics collisions whereas transient alignment relaxation time is tie…
Etude théorique de spectres de molécules toupies sphériques à l'aide du formalisme d'ensembles tensoriels irréductibles
2022
Vibrational-rotational spectroscopy of molecules of the spherical top type, in particular, SiH4 and GeH4 molecules, as well as their isotopologues, is of interest in various fields of science and technology, especially in astrophysics and planetology. One of the most important discoveries in the study of the atmospheres of giant planets is the discovery of german and silane gases in the atmospheres of Saturn, Titan, and Jupiter. Despite many years of research on the vibrational-rotational spectra of molecules of german, silane, and their deuterated modifications, many spectral ranges are still unexplored. However, a complete study of the atmospheres of giant planets is possible only in the …
Préparation de liposomes fonctionnels pour l’encapsulation de composés bioactifs ou de sondes moléculaires fluorescentes pour l’imagerie cellulaire
2016
At ICMUB Institute, SUV liposomes have been used to achieve fluorophore encapsulation (subphtalocyanine) for cellular imaging [1] and have been bioconjugated to a peptide (bombesin) to achieve site-specificity, thanks to the structural modification of cholesterol, a component of the liposome, upon introduction of a reactive function. Hence, such liposomes fonctionnalised on the outer face may react with the terminal function of the peptide. Upon purification of the liposome by FPLC a 15 % encapsulation rate was measured by UV/Vis and attempted by ICP. The (outer) diameter of the liposomes (dDLS and dMET) ranged between 20 and 60 nm depending on the type of function or substituents on the ou…
Formation de molécules dans des gaz atomiques ultra-froids par des champs quasi-résonnants
2010
We study the nonlinear mean-field dynamics of diatomic molecule formation at coherent photo- and magneto-association of ultracold atoms focusing on the case when the system is initially in the all-atomic state. We show that in the limit of strongly nonlinear interaction between an ultra-cold atomic-molecular system and a quasi-resonant electromagnetic field, the molecule formation process, depending on the characteristics of the associating field, may evolve according two different scenarios, namely, weak- and strong-oscillatory regimes. In the first case the number of molecules increases without pronounced oscillations of atom-molecule populations, while in the second case high-amplitude R…
Ultrafast optics in coherently spinning molecules
2020
This thesis reports on the study of unidirectional rotation of molecules and focuses on the rotational Doppler effect occuring in the course of third-harmonic generation in coherently spinning molecules.The rotational Doppler effect appears when a circularly polarized wave interacts with an anisotropic rotating object. During the interaction, an exchange of angular momentum and energy between the field and the object occurs, leading to a frequency shift of the wave. In this work, the frequency shift of the third-harmonic generated in unidirectionaly rotating molecules has been observed. An anlytical model developped in the mansucript forsees four kinds of frequency shifts depending on the m…
"Expanded" local mode approach and isotopic effect in polyatomic molecules
2014
In this thesis, on the base of the "expanded", local mode approach and general isotopic substitution theory we obtain sets of simple analytical relations between spectroscopic parameters (harmonic frequencies, anharmonic coefficients, ro-vibrational parameters, different kinds of Fermi and Coriolis-type interaction parameters) of the CH2D2, CH3D and CHD3 molecules. All of them are expressed as simple functions of spectroscopic parameters of the mother CH4 molecule. Test calculations with the isotopic relations show that even without including prior informations about the isotopic species, numerical results of calculations are in a good agreement both with experimental data and results of ab…