Coacervation of α-elastin studied by ultrafast nonlinear infrared spectroscopy

Elastin is the main protein to confer elasticity to biological tissues, through the formation of a hierarchical network of fibres.

Synchronous bilateral testicular germ cell tumour: case report and review of the literature

We report a case of a 30 years old male affected by synchronous bilateral germ cell tumor with a history of unilateral cryptorchidism; the patient underwent surgical treatment followed by adjuvant radiotherapy on paraaortic and iliac lymphnodes. Patients with synchronous tumors usually present with a higher stage disease in contrast to those with unilateral testicular carcinoma, yet the prognosis remains equally favorable.

Identification of the Excited-State C═C and C═O Modes of trans-β-Apo-8'-carotenal with Transient 2D-IR-EXSY and Femtosecond Stimulated Raman Spectroscopy

Assigning the vibrational modes of molecules in the electronic excited state is often a difficult task. Here we show that combining two nonlinear spectroscopic techniques, transient 2D exchange infrared spectroscopy (T2D-IR-EXSY) and femtosecond stimulated Raman spectroscopy (FSRS), the contribution of the C═C and C═O modes in the excited-state vibrational spectra of trans-β-apo-8'-carotenal can be unambiguously identified. The experimental results reported in this work confirm a previously proposed assignment based on quantum-chemical calculations and further strengthen the role of an excited state with charge-transfer character in the relaxation pathway of carbonyl carotenoids. On a more general ground, our results highlight the potentiality of nonlinear spectroscopic methods based on the combined use of visible and infrared pulses to correlate structural and electronic changes in photoexcited molecules.

Dynamics of the time-resolved stimulated Raman scattering spectrum in presence of transient vibronic inversion of population on the example of optically excited trans-β-apo-8'-carotenal

We have studied the effect of transient vibrational inversion of population in trans-β-apo-8(')-carotenal on the time-resolved femtosecond stimulated Raman scattering (TR-FSRS) signal. The experimental data are interpreted by applying a quantum mechanical approach, using the formalism of projection operators for constructing the theoretical model of TR-FSRS. Within this theoretical frame we explain the presence of transient Raman losses on the Stokes side of the TR-FSRS spectrum as the effect of vibrational inversion of population. In view of the obtained experimental and theoretical results, we conclude that the excited S2 electronic level of trans-β-apo-8(')-carotenal relaxes towards the S0 ground state through a set of four vibrational sublevels of S1 state.

Monitoring the intramolecular charge transfer process in the Z907 solar cell sensitizer: a transient Vis and IR spectroscopy and ab initio investigation

The excited state dynamics of Z907 in solution and on semiconductor substrates has been studied with ultrafast UV/Vis and IR spectroscopy and DFT/TDDFT calculations.

Picosecond optical parametric generator and amplifier for large temperature-jump

An optical parametric generator and amplifier producing 15 ps pulses at wavelengths tunable around 2 μm, with energies up to 15 mJ/pulse, has been realized and characterized. The output wavelength is chosen to match a vibrational combination band of water. By measuring the induced birefringence changes we prove that a single pulse is able to completely melt samples of ice in the 10⁻⁶ cm³ volume range, both at room pressure (263 K) and at high pressure (298 K, 1 GPa) in a sapphire anvil cell. This source opens the possibility of studying melting and freezing processes by spectroscopic probes in water or water solutions in a wide range of conditions as found in natural environments.

Connecting the Water Phase Diagram to the Metastable Domain: High-Pressure Studies in the Supercooled Regime

Pressure is extremely efficient to tune intermolecular interactions, allowing the study of the mechanisms regulating, at the molecular level, the structure and dynamics of condensed phases. Among the simplest molecules, water represents in many respects a mystery despite its primary role in ruling most of the biological, physical, and chemical processes occurring in nature. Here we report a careful characterization of the dynamic regime change associated with low-density and high-density forms of liquid water by measuring the line shape of the OD stretching mode of HOD in liquid water along different isotherms as a function of pressure. Remarkably, the high-pressure studies have been here extended down to 240 K, well inside the supercooled regime. Supported by molecular dynamics simulations, a correlation among amorphous and crystalline solids and the two different liquid water forms is attempted to provide a unified picture of the metastable and thermodynamic regimes of water.

Combination of transient 2D-IR experiments and ab initio computations sheds light on the formation of the charge-transfer state in photoexcited carbonyl carotenoids

The excited state dynamics of carbonyl carotenoids is very complex because of the coupling of single- and doubly excited states and the possible involvement of intramolecular charge-transfer (ICT) states. In this contribution we employ ultrafast infrared spectroscopy and theoretical computations to investigate the relaxation dynamics of trans-8'-apo-β-carotenal occurring on the picosecond time scale, after excitation in the S2 state. In a (slightly) polar solvent like chloroform, one-dimensional (T1D-IR) and two-dimensional (T2D-IR) transient infrared spectroscopy reveal spectral components with characteristic frequencies and lifetimes that are not observed in nonpolar solvents (cyclohexane). Combining experimental evidence with an analysis of CASPT2//CASSCF ground and excited state minima and energy profiles, complemented with TDDFT calculations in gas phase and in solvent, we propose a photochemical decay mechanism for this system where only the bright single-excited 1Bu(+) and the dark double-excited 2Ag(-) states are involved. Specifically, the initially populated 1Bu(+) relaxes toward 2Ag(-) in 200 fs. In a nonpolar solvent 2Ag(-) decays to the ground state (GS) in 25 ps. In polar solvents, distortions along twisting modes of the chain promote a repopulation of the 1Bu(+) state which then quickly relaxes to the GS (18 ps in chloroform). The 1Bu(+) state has a high electric dipole and is the main contributor to the charge-transfer state involved in the dynamics in polar solvents. The 2Ag(-) → 1Bu(+) population transfer is evidenced by a cross peak on the T2D-IR map revealing that the motions along the same stretching of the conjugated chain on the 2Ag(-) and 1Bu(+) states are coupled.

Role of local structure and dynamics of small ligand migration in proteins: a study of a mutated truncated hemoprotein from Thermobifida fusca by time resolved MIR spectroscopy

Carbon monoxide recombination dynamics in a mutant of the truncated hemoglobin from Thermobida fusca (3F-Tf-trHb) has been analyzed by means of ultrafast Visible-pump/MidIR-probe spectroscopy and compared with that of the wild-type protein. In 3F-Tf-trHb, three topologically relevant amino acids, responsible for the ligand stabilization through the formation of a H-bond network (TyrB10 TyrCD1 and TrpG8), have been replaced by Phe residues. X-ray diffraction data show that Phe residues in positions B10 and G8 maintain the same rotameric arrangements as Tyr and Trp in the wild-type protein, while Phe in position CD1 displays significant rotameric heterogeneity. Photodissociation of the ligand has been induced by exciting the sample with 550 nm pump pulses and the CO rebinding has been monitored in two mid-IR regions respectively corresponding to the ν(CO) stretching vibration of the iron-bound CO (1880-1980 cm(-1)) and of the dissociated free CO (2050-2200 cm(-1)). In both the mutant and wild-type protein, a significant amount of geminate CO rebinding is observed on a subnanosecond time scale. Despite the absence of the distal pocket hydrogen-bonding network, the kinetics of geminate rebinding in 3F-Tf-trHb is very similar to the wild-type, showing how the reactivity of dissociated CO toward the heme is primarily regulated by the effective volume and flexibility of the distal pocket and by caging effects exerted on the free CO on the analyzed time scale.

Structure and Dynamics of Low-Density and High-Density Liquid Water at High Pressure

Liquid water has a primary role in ruling life on Earth in a wide temperature and pressure range as well as a plethora of chemical, physical, geological, and environmental processes. Nevertheless, a full understanding of its dynamical and structural properties is still lacking. Water molecules are associated through hydrogen bonds, with the resulting extended network characterized by a local tetrahedral arrangement. Two different local structures of the liquid, called low-density (LDW) and high-density (HDW) water, have been identified to potentially affect many different chemical, biological, and physical processes. By combining diamond anvil cell technology, ultrafast pump-probe infrared spectroscopy, and classical molecular dynamics simulations, we show that the liquid structure and orientational dynamics are intimately connected, identifying the P-T range of the LDW and HDW regimes. The latter are defined in terms of the speeding up of the orientational dynamics, caused by the increasing probability of breaking and reforming the hydrogen bonds.

Ultrafast resonance energy transfer in the umbelliferone–alizarin bichromophore

Fast and efficient intramolecular energy transfer takes place in the umbelliferone–alizarin bichromophore; the process is well described by the Förster mechanism.

The role of stimulated Raman scattering in supercontinuum generation in bulk diamond

We report on experimental results of supercontinuum generation in bulk diamond. The spectrum of supercontinuum generated with 800 nm pump extends up to 600 nm towards short wavelengths. We present the numerical model explaining the phenomenon, in which the role of different nonlinear effects including stimulated Raman scattering is discussed. Unlike in other materials, in diamond the feature of supercontinuum due to stimulated Raman response is apparently visible.

Carbon monoxide recombination dynamics in truncated hemoglobins studied with visible-pump midIR-probe spectroscopy

Carbon monoxide recombination dynamics upon photodissociation with visible light has been characterized by means of ultrafast visible-pump/MidIR probe spectroscopy for the truncated hemoglobins from Thermobifida fusca and Bacillus subtilis. Photodissociation has been induced by exciting the sample at two different wavelengths: 400 nm, corresponding to the heme absorption in the B-band, and 550 nm, in the Q-bands. The bleached iron-CO coordination band located at 1850-1950 cm(-1) and the free CO absorption band in the region 2050-2200 cm(-1) have been observed by probe pulses tuned in the appropriate infrared region. The kinetic traces measured at 1850-1950 cm(-1) reveal multiexponential subnanosecond dynamics that have been interpreted as arising from fast geminate recombination of the photolyzed CO. A compared analysis of the crystal structure of the two proteins reveals a similar structure of their distal heme pocket, which contains conserved polar and aromatic amino acid residues closely interacting with the iron ligand. Although fast geminate recombination is observed in both proteins, several kinetic differences can be evidenced, which can be interpreted in terms of a different structural flexibility of the corresponding heme distal pockets. The analysis of the free CO band-shape and of its dynamic evolution brings out novel features about the nature of the docking site inside the protein cavity.

Multiple ipsilateral renal tumors: retrospective analysis of surgical and oncological results of tumor enucleation vs radical nephrectomy

AIMS

To evaluate the role of nephron-sparing surgery (NSS) compared to radical nephrectomy (RN) for treating multiple ipsilateral renal tumors.

METHODS

We retrospectively reviewed the clinical and pathological data of 960 patients who had surgery for pathologically confirmed RCC between 1986 and 2006. Thirty-four patients were diagnosed as having at least one ipsilateral smaller solid lesion associated with the primary RCC: 22 had RN while 12 had NSS for tumor enucleation.

RESULTS

All patients who had NSS had tumors confined within the kidney, as did 82% of patients treated with RN. The sole presence of concomitant accompanying benign histology to the primary RCC was diagnosed in 20% of patients. The mean (median, range) follow-up for patients treated with RN and NSS was 69 (58, 12-214) and 58 (44, 12-151) months. Tumor stage was significantly associated with tumor-specific survival (TSS) in the RN group (p<0.001). None of the patients who had tumor enucleation had positive surgical margins. Two patients recurred locally after NSS, elsewhere in the kidney, resulting in a crude ipsilateral recurrence rate of 17%. The analysis of TSS for patients with multiple ipsilateral tumors with a pT1 primary lesion showed no statistically significant differences between patients who had RN or NSS. Two patients had contralateral recurrence, resulting in a crude rate of 6%.

CONCLUSIONS

For patients with multiple ipsilateral renal tumors, 20% of the satellite lesions are benign and 6% develop a contralateral metachronous recurrence. We also observed similar TSS for patients treated with NSS and RN.