Impact of the Conformational Variability of Oligopeptides on the Computational Prediction of Their CD Spectra.

Although successful in the structural determination of ordered biomolecules, the spectroscopic investigation of oligopeptides in solution is hindered by their complex and rapidly changing conformational ensemble. The measured circular dichroism (CD) spectrum of an oligopeptide is an ensemble average over all microstates, severely limiting its interpretation, in contrast to ordered biomolecules. Spectral deconvolution methods to estimate the secondary structure contributions in the ensemble are still mostly based on databases of larger ordered proteins. Here, we establish how the interpretation of CD spectra of oligopeptides can be enhanced by the ability to compute the same observable from a set of atomic coordinates. Focusing on two representative oligopeptides featuring a known propensity toward an α-helical and ß-hairpin motif, respectively, we compare and cross-validate the structural information coming from deconvolution of the experimental CD spectra, sequence-based de novo structure prediction, and molecular dynamics simulations based on enhanced sampling methods. We find that small conformational variations can give rise to significant changes in the CD signals. While for the simpler conformational landscape of the α-helical peptide de novo structure prediction can already give reasonable agreement with the experiment, an extended ensemble of conformers needs to be considered for the ß-hairpin sequence.

Concurrent chemo-radiotherapy with taxotere and cisplatin in head and neck cancer: a feasibility study.

BACKGROUND: For many years surgery was the cornerstone of treatment for head and neck cancers and radiotherapy was the treatment of choice in adjuvant and advanced inoperable settings. Recently, induction sequential chemotherapy followed by radiotherapy has shown good tolerability and has prolonged the median overall survival. This phase II trial explored the feasibility of the concurrent association with radiotherapy of a full-dose chemotherapy based on an original schedule of docetaxel and cisplatin. PATIENTS AND METHODS: Twenty-four patients with head and neck squamous cell carcinoma (HNSCC) were enrolled. Taxotere (docetaxel) was administered on day 1, weekly for 6 weeks. The dose was 33 mg/m2 /w. Cisplatin was administered on day 2 at the dose of 70 mg/m2. Radiotherapy delivered was 60 Gy divided in 30 administrations over 6 weeks. RESULTS AND CONCLUSION: This schedule of treatment for HNSCC proved feasible. Appropriate support treatment, however, appears to be necessary for the feasibility of this concurrent chemo-radiotherapy.

Concurrent radio-chemotherapy with docetaxel and cisplatinum in inoperable or relapsed head and neck cancer.

Usually head and neck cancer is treated with combined therapy, applying surgery, if possible, and then radiotherapy and chemotherapy in a sequential or concomitant way. Sequential approach seems to be preferred, because of the high toxicity rate of concomitant therapy. Platinum compounds and 5-fluorouracil are the standard drugs, but new drugs are entering therapeutic arena: gemcitabine and taxanes are the most promising ones. The efficacy of these drugs, especially in association with radiotherapy, must be assessed; moreover it is essential to ascertain how to associate these drugs to radiotherapy and to evaluate drug toxicity when combined with the latter. End point of the study here presented is a preliminar assessment of toxicity and feasibility of concurrent radio-chemoterapy with docetaxel and cisplatinum in patients with head and neck cancer. The number of enrolled patients and the relatively short time of follow up do not allow to evaluate treatment efficacy.

Progressive multifocal leukoencephalopathy in a child with hyperimmunoglobulin E recurrent infection syndrome and review of the literature.

Progressive multifocal leukoencephalopathy (PML) is a fatal demyelinating disease due to infection with polyomavirus JC (JCV). PML occurs almost exclusively in immunocompromised patients, and although it has increased markedly in relation to AIDS, remains exceptional in children. We present the case of an immunocompromised child with hyperimmunoglobulin E recurrent infection syndrome (HIES) and pathologically-proven PML. HIES is a rare congenital immunodeficiency that to our knowledge has never before been reported in association with neurological complications. Following a recurrence of bronchopneumonia, the child's motor and cognitive functions deteriorated progressively in parallel with alterations on cerebral MRI. The neurological onset coincided with lymphocyte subset changes. PCR for JCV DNA did not detect the virus in CSF, and brain biopsy was required to secure the diagnosis. Antiviral treatment with cidofovir produced no benefit. Autopsy revealed the typical neuropathological findings of PML which were associated with inflammatory eosinophilic infiltrate (a marker of HIES). In accordance with the few pediatric PML cases reported and here reviewed, the child died five months after neurological onset.