Nanoporous sol-gel glasses were used as host materials for the encapsulation of apomyoglobin, a model protein employed to probe in a rational manner the important factors that influence the protein conformation and stability in silica-based materials. The transparent glasses were prepared from tetramethoxysilane (TMOS) and modified with a series of mono-, di- and tri-substituted alkoxysilanes, R(n)Si(OCH(3))(4-n)(R= methyl-, n = 1; 2; 3) of different molar content (5; 10; 15%) to obtain the decrease of the siloxane linkage (-Si-O-Si-). The conformation and thermal stability of apomyoglobin characterized by circular dichroism spectroscopy (CD) was related to the structure of the silica host matrix characterized by (29)Si MAS NMR and N(2) adsorption. We observed that the protein transits from an unfolded state in unmodified glass (TMOS) to a native-like helical state in the organically-modified glasses, but also that the secondary structure of the protein was enhanced by the decrease of the siloxane network with the methyl modification (n=0 <n=1 <n=2 <n=3; 0 <5 <10 <15 mol %). In 15% trimethyl-modified glass, the protein even reached a maximum molar helicity (-24,000 deg. cm(2) mol(-1)) comparable to the stable folded heme-bound haloprotein in solution. The protein conformation and stability induced by the change of its microlocal environment (surface hydration, crowding effects, microstructure of the host matrix) were discussed owing to this trend dependency. These results can have an important impact for the design of new efficient biomaterials (sensors or implanted devices) in which properly folded protein is necessary.(c) 2009 Wiley Periodicals, Inc. Biopolymers, 2009.

Increasing evidence suggests that cancer is a disease in which the persistence of the tumor relies on a small population of tumor-initiating cells, the so called tumor stem cells (TSC). Only these cells are capable of self-renewal and thereby possess the ability for unlimited proliferation. One reason for the inability of conventional tumor treatments to achieve long-term cures seems to be that TSC are resistant to many therapeutic approaches. A detailed characterization of TSC should have a substantial impact on the optimization of therapeutic protocols. While TSC in hematopoietic malignancies have been most intensively studied, subpopulations with stem cell properties have been identified in some solid tumors including breast carcinomas, gliomas and melanomas. In case of melanoma, however, a clear-cut molecular characterization is still pending. Considerable research is needed to establish standard procedures for the isolation of melanoma stem cells to facilitate determining how these cells, critical for tumor persistence and progression, can be effectively eliminated. A pressing question is if melanoma stem cells are in principle sensitive to immunotherapy.

UV light provokes DNA lesions that interfere with replication and transcription. These lesions may compromise cell viability and usually are removed by nucleotide excision repair (NER). In humans, inactivation of NER is associated with three rare autosomal recessive inherited disorders: xeroderma pigmentosum (XP), Cockayne syndrome, and trichothiodystrophy. The NER earliest step is lesion recognition by a complex formed by XPC and HHR23B proteins. In a subsequent step, XPA protein becomes associated to the repair complex. Here we investigate whether XPA and XPC proteins, involved in global genome repair, may contribute to a signal transduction pathway regulating the response to UVC-induced lesions. We monitored the expression of several UVC-induced genes in cells deficient in either a transduction pathway or mutated on an NER gene. Expression of the KIN17 gene is induced after UVC irradiation independently of p53 and of activating transcription factor 2. However, in human cells derived from XPA or XPC patients the UVC-induced accumulation of KIN17 RNA and protein is abolished. Our results indicate that the presence of functional XPA and XPC proteins is essential for the up-regulation of the KIN17 gene after UVC irradiation. They also show that the integrity of global genome repair is required to trigger KIN17 gene expression and probably other UVC-responsive genes.