Time-resolved single-crystal X-ray crystallography

In this chapter the development of time-resolved crystallography is traced from its beginnings more than 30 years ago. The importance of being able to “watch” chemical processes as they occur rather than just being limited to three-dimensional pictures of the reactant and final product is emphasised, and time-resolved crystallography provides the opportunity to bring the dimension of time into the crystallographic experiment. The technique has evolved in time with developments in technology: synchrotron radiation, cryoscopic techniques, tuneable lasers, increased computing power and vastly improved X-ray detectors. The shorter the lifetime of the species being studied, the more complex is the experiment. The chapter focusses on the results of solid-state reactions that are activated by light, since this process does not require the addition of a reagent to the crystalline material and the single-crystalline nature of the solid may be preserved. Because of this photoactivation, time-resolved crystallography is often described as “photocrystallography”. The initial photocrystallographic studies were carried out on molecular complexes that either underwent irreversible photoactivated processes where the conversion took hours or days. Structural snapshots were taken during the process. Materials that achieved a metastable state under photoactivation and the excited (metastable) state had a long enough lifetime for the data from the crystal to be collected and the structure solved. For systems with shorter lifetimes, the first time-resolved results were obtained for macromolecular structures, where pulsed lasers were used to pump up the short lifetime excited state species and their structures were probed by using synchronised X-ray pulses from a high-intensity source. Developments in molecular crystallography soon followed, initially with monochromatic X-ray radiation, and pump-probe techniques were used to establish the structures of photoactivated molecules with lifetimes in the micro- to millisecond range. For molecules with even shorter lifetimes in the sub-microsecond range, Laue diffraction methods (rather than using monochromatic radiation) were employed to speed up the data collections and reduce crystal damage. Future developments in time-resolved crystallography are likely to involve the use of XFELs to complete “single-shot” time-resolved diffraction studies that are already proving successful in the macromolecular crystallographic field.</p

Synthesis and Characterization of the Thermoelectric Nickel Tetrathiooxalate Polymer as Nanoparticles

International audienceNanoparticles of the conductive coordination polymer Ni(tto) have been synthesized under mild conditions in the presence of bio-based polyesters or polyethylene glycol acting as growth controlling agents. With polyesters, aggregates of particles are observed whereas well dispersed nanoparticles are obtained with polyethylene glycol. Indeed, for a Ni2+/polyethylene glycol weight ratio of 0.031, transmission electron micrographs evidence dispersed particles exhibiting sizes in the 3 - 10 nm range. Infrared spectra for nanopowders show two CS stretching modes in the 1100 - 1190 cm−1 range, confirming the presence of the tetrathiooxalate ligand coordinated to the nickel center. The room-temperature electrical conductivity for the nanopowder prepared in the presence of polyethylene glycol is about 0.8 S∙cm−1, a decent value for tetrathiolate-based polymers. Finally, magnetic susceptibility measurements for well-dispersed Ni(tto) particles evidence a Curie-Weiss law in a large temperature range. Moreover, low temperatures measurement would confirm intra- or interchain interactions between nickel atoms within the Ni(tto) polymer chains

Soluble CD70: a novel immunotherapeutic agent for experimental glioblastoma

Object Given the overall poor outcome with current treatment strategies in malignant gliomas, immunotherapy has been considered a promising experimental approach to glioblastoma for more than 2 decades. A cell surface molecule, CD70, may induce potent antitumor immune responses via activation of the costimulatory receptor CD27 expressed on immune effector cells. There is evidence that a soluble form of CD70 (sCD70) may exhibit biological activity, too. A soluble costimulatory ligand is attractive because it may facilitate immune activation and may achieve a superior tissue distribution. Methods To test the antiglioma effect of sCD70, the authors genetically modified SMA-560 mouse glioma cells to secrete the extracellular domain of CD70. They assessed the immunogenicity of the transfected cells in cocultures with immune effector cells by the determination of immune cell proliferation and the release of interferon-gamma. Syngeneic VM/Dk mice were implanted orthotopically with control or sCD70-releasing glioma cells to determine a survival benefit mediated by sCD70. Depletion studies were performed to identify the cellular mediators of prolonged survival of sCD70-releasing glioma-bearing mice. Results The authors found that ectopic expression of sCD70 enhanced the proliferation and interferon-gamma release of syngeneic splenocytes in vitro. More importantly, sCD70 prolonged the survival of syngeneic VM/Dk mice bearing intracranial SMA-560 gliomas. The survival rate at 60 days increased from 5 to 45%. Antibody-mediated depletion of CD8-positive T cells abrogates the survival advantage conferred by sCD70. Conclusions These data suggest that sCD70 is a potent stimulator of antiglioma immune responses that depend critically on CD8-positive T cells. Soluble CD70 could be a powerful adjuvant for future immunotherapy trials for glioblastoma

Collision Tumor of Primary Laryngeal Mucosal Melanoma and Invasive Squamous Cell Carcinoma with IL-17A and CD70 Gene Over-Expression

The most common primary malignancy of the larynx is the squamous cell carcinoma (SCC). The primary malignant melanoma is quite rare in this location. Less than 60 cases of laryngeal melanomas have been reported to date. To our knowledge, collision primary malignant melanoma and invasive squamous cell carcinoma in the vocal cords has not been reported. We report a 53-year-old male patient who was diagnosed with a collision tumor of laryngeal melanoma and invasive SCC. Multiple Th17 pathway related genes including CTLA-4, IL-17A-F, PLZF, FoxP3, RorγT, CD27, and CD70 were analyzed by reverse transcriptase-polymerase chain reaction (Rt–PCR) in this case. Both IL-17A and CD70 genes were detected in this case of collision tumor. The results may define useful biomarkers for early diagnosis of mucosal melanoma and open an immunotherapeutic field for clinical management with the potential benefit from the immunomodulators that enhance both genes