Claudia Sadun

Overview of the main methods used to combine proteins with nanosystems: absorption, bioconjugation, and encapsulation.

The latest development of protein engineering allows the production of proteins having desired properties and large potential markets, but the clinical advances of therapeutical proteins are still limited by their fragility. Nanotechnology could provide optimal vectors able to protect from degradation therapeutical biomolecules such as proteins, enzymes or specific polypeptides. On the other hand, some proteins can be also used as active ligands to help nanoparticles loaded with chemotherapeutic or other drugs to reach particular sites in the body. The aim of this review is to provide an overall picture of the general aspects of the most successful approaches used to combine proteins with nanosystems. This combination is mainly achieved by absorption, bioconjugation and encapsulation. Interactions of nanoparticles with biomolecules and caveats related to protein denaturation are also pointed out. A clear understanding of nanoparticle-protein interactions could make possible the design of precise and versatile hybrid nanosystems. This could further allow control of their pharmacokinetics as well as activity, and safety.

Palladium (II) and platinum (II) aqueous solutions. Evidence for the solvation of the [PdCl4]2− and [PtCl4]2− ions

Abstract The isomorphic substitution applied to solutions of NH4PtCl4 and NH4PdCl4 allows to show the existence of 2 bound water molecules at the apical sites of PtCl42− and PdCl42− ions. The Pt(Pd)-H2O distance results equal to 2.77 A.

A new technique for the study of phase transitions by means of energy dispersive x-ray diffraction. Application to polymeric samples

A new application of energy dispersive x-ray diffraction to the kinetics of phase transitions is reported. The aim of this work is to provide a new investigation tool to follow the evolution of polymeric systems from the initial to the final phase. The theoretical treatment is developed both for constant density transitions and for the variable density ones. The experimental route is illustrated by an example.

Ab initio SCF study on LiClO4 and Li2SO4 molecules: Geometries and vibrational frequencies

Abstract The coordination structures of the molecules LiClO4 and Li2SO4 were studied by ab initio SCF calculations carried out at the 3-21G*, 6-31G* and DZP basis sets level; the geometries of ClO4− and SO42− were determined at the 3-21G*, 6-31G*, 6-31 + G*, DZP and TZP levels. LiClO4 and Li2SO4 prefer at all the levels of the HF-SCF theory bidentate structures of C2v and D2d symmetries, respectively. The tridentate and monodentate C3v, symmetry structures of LiClO4, and the C2v and tridentate C3v ones of Li2SO4 were also considered in detail. Harmonic frequencies of vibration of the anions and of each coordination model of LiClO4 and Li2SO4 as well as the 18O spectra of LiClO4 (C2v symmetry) and Li2SO4 (D2d symmetry) are reported and commented on using the experimental IR spectroscopy results.

Molecular aggregation phenomena in solution: an energy dispersive X-ray diffraction study of concentrated imidazole water solutions

Abstract An energy dispersive X-ray diffraction study of concentrated imidazole water solutions is reported. It reveals the presence of extended solute–solute aggregates. Such results can be interpreted in terms of a branch of a pseudo-helix of imidazole dimers interacting with water molecules. The mean distance between molecules in the dimer is ∼3.7 A, while the mean distance between dimers is 4.75–4.95 A depending on concentration. The model structure functions and theoretical radial distribution functions fit the experimental data.

Ab initio SCF study of the BO−2 ion and the NaBO2 and HBO2 molecules

Abstract The results of ab initio molecular orbital calculations on the BO − 2 anion and on the NaBO 2 and HBO 2 molecules are presented and discussed. NaBO 2 is a linear molecule of C ∞ v symmetry and its transition state corresponds to a cyclic structure with a bent BO − 2 group. Preference for an angular structure of C 8 symmetry is suggested for HBO 2 . The results of this study are compared with previous theoretical and vibrational spectroscopy investigations. Limited pseudo-potential calculations are also reported for BO − 2 and the linear structure of NaBO 2 .

Crystallization kinetics of PEO-alkaline perchlorate solutions observed by energy dispersive x-ray diffraction

The crystallization kinetics of poly(ethylene oxide) doped with various alkaline perchlorate salts were measured at room temperature by means of the new energy dispersive x-ray diffraction method for the phase transition. The experimental points of the transformation coordinate were fitted using the phenomenological Liquori-Tripiciano law, the parameters of which were evaluated for each case. The influence of the concentration and of the cation dimensions on the crystallization rate is discussed. Further details about the application of this nonconventional diffractometric technique to polymers are also reported, as is an intuitive model for describing the method.

XPS and LAXS study of 1,3-thiazolidine-2-thione and its complexes with Co(II) and Zn(II)

Abstract Metal complexes of general formula M(ttz) 2 X 2 (with M = Zn(II) or Co(II); X = Cl or Br; ttz = 1,3-thiazolidine-2-thione) have been synthetized as crystalline (Br and Cl) and amorphous (chloride derivative only) compounds. LAXS (Large Angle X-ray Scattering) investigations reveal that the ttz ligand is bonded to the zinc or cobalt ion through one of the two sulphur atoms and no metal-nitrogen bonds are present. Detailed XPS (X-ray Photoelectron Spectroscopy) studies show that ttz is bonded to the metal through the thioketonic sulphur atom and that electronic charge redistribution in the ligand takes place after complexation.

Synthesis and characterization of a cobalt(III) complex with 1-(d-3-mercapto-2-methylpropionyl)-l-proline

The reaction of CoCl2 with 1-(D-3-mercapto-2-methylpropionyl)-L-proline (L or captopril) yields a new nanocrystalline complex with general formula [CoL2(OH)]2. The complex has been characterised with infrared (IR) and ultra-violet visible (UV-vis) spectroscopies, magnetic measurements, X-ray photoelectron spectroscopy (XPS), and wide angle X-ray scattering (WAXS). XPS analyses is a valuable tool for studying the chemical composition and the chemical state of elements at the surface of solids whereas WAXS provides information on the short range order. A model is proposed for the binding of the complex and its structure: the Co(III) ion is bonded with a pseudo-octahedral configuration. Captopril molecules are coordinated via mercapto group and amidic C=O group to Co(III) ions: two S atoms are bridging bonded between two Co(III) ions. The OH- ion completes the coordination around the Co(III).

X-ray photoelectron spectra of complexes with 1-(D-3-mercapto-2-methylpropionyl)-L-proline and Ni(II), Cd(II) and Cu(I): synthesis and LAXS study of Cu(I) derivative.

Metal complexes of general formula Na2M(CAP)2xH2O (with M = Cd(II) or Ni(II), x = 7 and 4, respectively, CAP = 1-(D-3-mercapto-2-methylpropionyl)-L-proline) and NaCuCAPx3H2O have been synthesized as amorphous compounds and studied by means of X-ray photoelectron spectroscopy (XPS). Cu(I) derivative has been studied by IR, XPS and large-angle X-ray scattering (LAXS). IR data and the chemical shift of core level signals suggest that CAP is bonded to the metal via the sulphur atom and the carbonylic oxygen. LAXS data confirm this finding and are consistent with a tetrahedral configuration around the copper ion. The CAP molecule is bonded through the sulphur and the carbonylic oxygen and two water molecules complete the coordination around the metal. The sodium ion exhibits a tetrahedral configuration and interacts with the carboxylic group and two water molecules. One of these is bridging bonded between copper and sodium. No metal-nitrogen bonds are present.