Search

Upconverting nanoparticles (UCNPs) are a highly attractive tool owing to their unique property of showing visible luminescence when excited in the near-infrared (NIR) region. Plain UCNPs have no biorecognition capabilities, but functionalization of their surface with azido groups renders them conjugatable to ethynyl-modified oligonucleotides in a bioorthogonal fashion. Single-stranded DNA was covalently attached to the surface of UCNPs by click chemistry and purified by size exclusion chromatography (SEC) at elevated temperature. Covalent attachment was evidenced by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. DNA conjugation makes the particle soluble in water and enables it to recognize its counter strand. Such UCNPs are capable of nonspecifically crossing cell membranes. Confocal microscopy reveals the high potential of the bright UCNPs for live cell imaging in the NIR, where the UCNP–DNA conjugates can be considered to act as a kind of nano-sized lamp. Furthermore, cross-linking of those DNA nanolamps yields highly emissive aggregates.

Inhibitors of apoptosis proteins (IAPs) are a highly conserved class of multifunctional proteins. Rac1 is a well-studied Rho GTPase that controls numerous basic cellular processes. While the regulation of nucleotide binding to Rac1 is well understood, the molecular mechanisms controlling Rac1 degradation are not known. Here, we demonstrate X-linked IAP (XIAP) and cellular IAP1 (c-IAP1) directly bind to Rac1 in a nucleotide-independent manner to promote its polyubiquitination at Lys147 and proteasomal degradation. These IAPs are also required for degradation of Rac1 upon CNF1 toxin treatment or RhoGDI depletion. Consistently, downregulation of XIAP or c-IAP1 by various strategies led to an increase in Rac1 protein levels in primary and tumour cells, leading to an elongated morphology and enhanced cell migration. Further, XIAP counteracts Rac1-dependent cellular polarization in the developing zebrafish hindbrain and promotes the delamination of neurons from the normal tissue architecture. These observations unveil an evolutionarily conserved role of IAPs in controlling Rac1 stability thereby regulating the plasticity of cell migration and morphogenesis.

Aufkonvertierende lumineszierende Materialien sind in der Lage, nah-infrarotes Licht zu absorbieren und in kurzerwellige Lumineszenz umzuwandeln. Die Effizienz dieses bemerkenswerten Effekts ist stark temperaturabhangig, was die Temperaturmessung mit einer Ortsauflosung im Nanometerbereich ermoglicht. Alle bisher bekannten Aufkonvertierungs-Materialien zeigen mehrere (meistens zwei) schmale Emissionsbanden, jede mit einer eigenen Temperaturabhangigkeit. Das Verhaltnis der Intensitaten zweier dieser Banden ist ein selbstreferenziertes Signal zur optischen Temperaturmessung, beispielsweise in Zellen.

Upconverting materials are capable of absorbing near-infrared light and converting it into short-wavelength luminescence. The efficiency of this remarkable effect is highly temperature dependent and thus can be used for temperature determination (thermometry) on a nanometer scale. All the upconverting materials discovered so far display several (mainly two) narrow emission bands, each of which has its own temperature dependence. The ratio of the intensity of two of these bands provides a referenced signal for optical sensing of temperature, for example inside cells.