Theory and spectroscopy of dihydrogen endofullerenes

Recent advances in synthetic chemistry made available a new class of fascinatingcompounds in which a molecule of hydrogen is encased inside the hollow cavity ofthe highly symmetric fullerene C60. There is a great interest in studying endohedralfullerene complexes owing to the rigidity, symmetry, homogeneity and isolation providedby the carbon cages. On one side these properties result in very detailed and wellresolvedspectra even in the condensed phase. On the other side such supermoleculesare a unique real-world example of a quantum rotor confined in an almost spherical trap,whose dynamics can be directly and accurately treated from first principles. The studyof the quantum dynamics and the analysis of the spectroscopic observations of H2@C60provide a stepping stone for the characterization of the carbon-hydrogen interaction incurved nanocarbons.In this work symmetry is employed to simplify the analytical treatment of the dynamicsof the endohedral hydrogen, by expanding the non-bonding confining potentialin terms of spherical multipoles and by using a spherical basis to represent the effectiverotational-translational Hamiltonian. The thesis features the first study of an endohedralhydrogen fullerenes, H2@C60, by infrared spectroscopy . The quantization of thetranslational motion, the high rotational freedom and rotational-translational couplingsclearly show up in the infrared spectra. The successful assignment of the IR peaks totransitions between the quantum states of the confined hydrogen by means of the presentedtheoretical model has lead to the first accurate determination of the molecularvibro-rotational parameters and effective hydrogen-cage potentials in [email protected] nuclear spin dynamics is very sensitive to the local environment around thehydrogen molecules. Nuclear magnetic resonance spectroscopy at cryogenic temperaturesshows that the symmetry at the center of the cages is reduced by solid state effectsand/or occluded impurities. The observations of small but not yet completely understooddiscrepancies in the lineshapes and relaxations of two samples of H2@C60 stressthe influence of the preparation, storage and manipulation on the nuclear spin dynamicsof endohedral hydrogen fullerenes

Identification of hormonogenic tyrosines in fragment 1218-1591 of bovine thyroglobulin by mass spectrometry. Hormonogenic acceptor TYR-12donor TYR-1375.

A fragment of bovine thyroglobulin encompassing residues 1218-1591 was prepared by limited proteolysis with thermolysin and continuous-elution polyacrylamide gel electrophoresis in SDS. The reduced and carboxymethylated peptide was digested with endoproteinase Asp-N and fractionated by reverse-phase high performance liquid chromatography. The fractions were analyzed by electrospray and fast atom bombardment mass spectrometry in combination with Edman degradation. The post-translational modifications of all seven tyrosyl residues of the fragment were characterized at an unprecedented level of definition. The analysis revealed the formation of: 1) monoiodotyrosine from tyrosine 1234; 2) monoiodotyrosine, diiodotyrosine, triiodothyronine (T3), and tetraiodothyronine (thyroxine, T4) from tyrosine 1291; and 3) monoiodotyrosine, diiodotyrosine, and dehydroalanine from tyrosine 1375. Iodothyronine formation from tyrosine 1291 accounted for 10% of total T4 of thyroglobulin (0.30 mol of T4/mol of 660-kDa thyroglobulin), and 8% of total T3 (0.08 mol of T3/mol of thyroglobulin). This is the first documentation of the hormonogenic nature of tyrosine 1291 of bovine thyroglobulin, as thyroxine formation at a corresponding site was so far reported only in rabbit, guinea pig, and turtle thyroglobulin. This is also the first direct identification of tyrosine 1375 of bovine thyroglobulin as a donor residue. It is suggested that tyrosyl residues 1291 and 1375 may support together the function of an independent hormonogenic domain in the mid-portion of the polypeptide chain of thyroglobulin

Production of highly concentrated and hyperpolarized metabolites within seconds in high and low magnetic fields

Hyperpolarized metabolites are very attractive contrast agents for in vivo magnetic resonance imaging studies enabling early diagnosis of cancer, for example. Real-time production of concentrated solutions of metabolites is a desired goal that will enable new applications such as the continuous investigation of metabolic changes. To this end, we are introducing two NMR experiments that allow us to deliver high levels of polarization at high concentrations (50 mM) of an acetate precursor (55% 13C polarization) and acetate (17% 13C polarization) utilizing 83% para-state enriched hydrogen within seconds at high magnetic field (7 T). Furthermore, we have translated these experiments to a portable low-field spectrometer with a permanent magnet operating at 1 T. The presented developments pave the way for a rapid and affordable production of hyperpolarized metabolites that can be implemented in e.g. metabolomics labs and for medical diagnosis

Symmetry-breaking in the H2@C60endofullerene revealed by inelastic neutron scattering at low temperature

The fine structure of the rotational ground state of molecular ortho-hydrogen confined inside the fullerene cage C60 is investigated by inelastic neutron scattering (INS). The INS line corresponding to transitions between the three sub-levels comprising the ortho ground state to the non-degenerate para ground state was studied as a function of temperature down to 60 mK in neutron energy gain. The experiments show that at ambient pressure the three ortho sub-levels are split into a low energy non-degenerate level and a high energy doubly degenerate level separated by 0.135 ± 0.010 meV. This observation is consistent with hydrogen molecules being located at sites with axial symmetry superseding the icosahedral symmetry of isolated rigid C60 cages in the solid phase. To gain insight into the role of inter-cage interactions in determining the symmetry breaking potential, the effects of hydrostatic pressure on the fine structure of the line was also investigated. The analysis of the INS spectra shows that the potential and the energy levels of H2 are sensitive to the orientation of neighbouring cages, consistent with the low-temperature crystalline phase of C60

Experimental, theoretical and computational investigation of the inelastic neutron scattering spectrum of a homonuclear diatomic molecule in a nearly spherical trap: H2@C60

In this paper we report a methodology for calculating the inelastic neutron scattering spectrum of homonuclear diatomic molecules confined within nano-cavities of spherical symmetry. The method is based on the expansion of the confining potential into multipoles of the coupled rotational and translational angular variables. The Hamiltonian and the INS transition probabilities are evaluated analytically. The method affords a fast and computationally inexpensive way to simulate the inelastic neutron scattering spectrum of molecular hydrogen confined in fullerene cages. The potential energy surface is effectively parametrized in terms of few physical parameters comprising an harmonic term, anharmonic corrections and translation–rotation couplings. The parameters are refined by matching the simulations against the experiments and the excitation modes are identified for transfer energies up to 215 meV

The Endofullerene HF@C 60 : Inelastic Neutron Scattering Spectra from Quantum Simulations and Experiment, Validity of the Selection Rule and Symmetry Breaking

Accurate quantum simulations of the low-temperature inelastic neutron scattering (INS) spectra of HF@C60 are reported for two incident neutron wavelengths. They are distinguished by the rigorous inclusion of symmetry-breaking effects in the treatment and having the spectra computed with HF as the guest, rather than H2 or HD, as in the past work. The results demonstrate that the precedent-setting INS selection rule, originally derived for H2 and HD in near-spherical nanocavities, applies also to HF@C60, despite the large mass asymmetry of HF and the strongly mixed character of its translation–rotation eigenstates. This lends crucial support to the theoretical prediction made earlier that the INS selection rule is valid for any diatomic molecule in near-spherical nanoconfinement. The selection rule remains valid in the presence of symmetry breaking but is modified slightly in an interesting way. Comparison is made with the recently published experimental INS spectrum of HF@C60. The agreement is very good, apart from one peak for which our calculations suggest a reassignment. This reassignment is consistent with the measured INS spectrum presented in this work, which covers an extended energy range

Proteomic study of muscle sarcoplasmic proteins using AUT-PAGE/SDS-PAGE as two-dimensional gel electrophoresis

The conversion of muscle to meat in pig involves mainly proteolysis of myofibrillar proteins, which undergo notable changes since early stage of rigor mortis, even after 48 h post mortem. The tenderness of meat has been thoroughly investigated to understand the biochemical mechanisms, which influence texture and flavour development as well as the technological parameters and hence meat quality. Cytoplasmic proteolytic calcium dependent enzymes, named -and m-calpains, which act in the early stages of rigor mortis, significantly contribute to tenderization weakening myofibrils. These enzymes, however, act for fewdays because they are specifically inhibited by calpastatin and by pH lowering. However, when pH falls to about 5.0, proteolytic activity on muscle proteins is continued by longer acting lysosomal proteinase, cathepsins [3,7–9]. Post mortem proteolysis also causes relevant changes in sarcoplamic protein fraction, which represent the water soluble fraction (quantitatively about 30–35%) of meat total protein, and the involved proteins has already been identified by proteomic-based studies. Recent investigations have demonstrated that the most commonly found Lactobacillus species in dry fermented meats are able to hydrolyse myofibrillar and sarcoplasmic muscle proteins in vitro.The most abundant sarcoplasmic proteins, as mixture of basic polypeptides with a narrow spread range of molecular masses, represented an excellent model to test our analytical technique and to delineate its capabilities. In the present study, we compared 2D AUT-PAGE/SDSPAGE maps of water-soluble proteins extracted from fresh meat and from dry-cured ham, a non fermented product, from “Naples-type” salami, a microbiologically fermented product, and from “Coppa”, a typical semi-fermented product. Electrophoretically separated proteins have been identified by MALDI-ToF mass fingerprinting

Symmetry-breaking in the endofullerene H2O@C60 revealed in the quantum dynamics of ortho and para-water: a neutron scattering investigation

Inelastic neutron scattering (INS) has been employed to investigate the quantum dynamics of water molecules permanently entrapped inside the cages of C60 fullerene molecules. This study of the supramolecular complex, H2O@C60, provides the unique opportunity to study isolated water molecules in a highly symmetric environment. Free from strong interactions, the water molecule has a high degree of rotational freedom enabling its nuclear spin isomers, ortho-H2O and para-H2O to be separately identified and studied. The INS technique mediates transitions between the ortho and para spin isomers and using three INS spectrometers, the rotational levels of H2O have been investigated, correlating well with the known levels in gaseous water. The slow process of nuclear spin conversion between ortho-H2O and para-H2O is revealed in the time dependence of the INS peak intensities over periods of many hours. Of particular interest to this study is the observed splitting of the ground state of ortho-H2O, raising the three-fold degeneracy into two states with degeneracy 2 and 1 respectively. This is attributed to a symmetry-breaking interaction of the water environment

Imaging of hepatocellular carcinoma recurrence after liver transplantation

Liver transplantation (LT) provides the highest survival benefit to patients with unresectable hepatocellular carcinoma (HCC). The Milan criteria have been developed for the selection of LT candidates with the goal of improving survival and maintaining an acceptable risk of HCC recurrence. Despite this, recurrence of HCC after LT occurs in up to 20% of cases and represents a major concern due to the poor prognosis of these patients. Furthermore, several extended criteria for the selection of LT candidates have been proposed to account for the growing demand for organs and the resultant increase in the risk of HCC recurrence. Radiologists should be aware that HCC can recur after LT with multiple organ involvement. Knowledge of the location and radiologic appearance of recurrent HCC is necessary to ensure the choice of the most appropriate therapy. This paper aims to comprehensively summarize the spectrum of HCC recurrence after LT and to examine and discuss the imaging features of these lesions. CRITICAL RELEVANCE STATEMENT: This paper aims to share a review of imaging findings of HCC recurrence after LT and to make radiologists familiar with the spectrum of this disease

Nuclear magnetic resonance of hydrogen molecules trapped inside C70 fullerene cages

We present a solid-state NMR study of H2 molecules confined inside the cavity of C70 fullerene cages over a wide range of temperatures (300?K to 4?K). The proton NMR spectra are consistent with a model in which the dipole–dipole coupling between the ortho-H2 protons is averaged over the rotational/translational states of the confined quantum rotor, with an additional chemical shift anisotropy ?HCSA=10.1?ppm induced by the carbon cage. The magnitude of the chemical shift anisotropy is consistent with DFT estimates of the chemical shielding tensor field within the cage. The experimental NMR data indicate that the ground state of endohedral ortho-H2 in C70 is doubly degenerate and polarized transverse to the principal axis of the cage. The NMR spectra indicate significant magnetic alignment of the C70 long axes along the magnetic field, at temperatures below ~10?