Probing Macromolecular Conformation in Restricted Geometry by PEF: Application to Hydrophobically Modified PAMAM Dendrimers Isolated Inside Surfactant Micelles.

The conformation of a series of zero-generation polyamidoamine dendrimers end-labeled with four 1-pyrene-butyroyl, -hexanoyl, -octanoyl, -decanoyl, and -dodecanoyl derivatives, referred to as the PyCX-PAMAM-G0 samples with = 4, 6, 8, 10, and 12, respectively, was characterized in ,-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and aqueous solutions of 50 mM sodium dodecyl sulfate (SDS) or 50 mM dodecyltrimethylammonium bromide (DTAB). The conformation of the PyCX-PAMAM-G0 samples was determined from the global model-free analysis (MFA) of the fluorescence decays, which yielded the average rate constant (⟨⟩) for pyrene excimer formation (PEF) between an excited and a ground-state pyrenyl labels, with ⟨⟩ being proportional to the local concentration ([Py]) of the pyrenyl labels within the macromolecular volume; ⟨⟩-vs-[Py] plots yielded straight lines passing through the origin in DMF and DMSO, demonstrating that the internal segments of the dendrimers obeyed Gaussian statistics in these two solvents. In aqueous surfactant solutions, the hydrophobic pyrenyl labels induced the interactions of the PyCX-PAMAM-G0 dendrimers with the SDS and DTAB micelles.

Flexibility of Poly(alkyl methacrylate)s Characterized by Their Persistence Length Determined through Pyrene Excimer Formation.

A series of poly(alkyl methacrylate)s and poly(oligo(ethylene glycol) methyl ether methacrylate)s labeled with 1-pyrenebutanol were referred to as the PyC-PCMA samples with = 1, 4, 6, 8, 12, and 18 and the PyC-PEGMA samples with = 0-5, 9, 16, and 19, respectively. Pyrene excimer formation (PEF) upon the encounter between an excited and a ground-state pyrenyl labels was employed to determine their persistence length () in -xylene. The fluorescence decays of the PyC-PCMA and PyC-PEGMA samples were acquired and analyzed with the fluorescence blob model to yield the number () of structural units in the volume probed by an excited pyrenyl label.

Virtual social grooming in macaques and its psychophysiological effects.

Allogrooming is a widespread, pervasive activity among non-human primates. Besides its hygienic function, it is thought to be instrumental in maintaining social bonds and establishing hierarchical structures within groups. However, the question arises as to whether the physiological and social benefits derived from social touch stem directly from body stimulation, or whether other mechanisms come into play.