Processing of Fluorescence Lifetime Image Using Modified Phasor Approach: Homo-FRET from the Acceptor

As the hardware of FLIM technique becomes mature, the most important criterion for FLIM application is the correct interpretation of its data. In this research, first of all, a more orthogonal phasor approach, called as Modified Phasor Approach (MPA), is put forward. It is a way to calculate the lifetime of the complex fluorescent process, and a rule to measure how much the fluorescence process deviates from single exponential decay. Secondly, MPA is used to analysis the time-resolved fluorescence processes of the transfected CHO-K1 Cell lines expressing adenosine receptor A₁R tagged by CYP and YFP, measured in the channel of the acceptor. The image of the fluorescence lifetime and the multiplication of the fluorescence lifetime and deviation from single exponential decay reveal the details of the Homo-FRET. In one word, MPA provides the physical meaning in its whole modified phasor space, and broadens the way for the application of the fluorescence lifetime imaging.     

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Chemical and mechanical properties of snake fangs

The composition of dental tissues and their interaction determines its mechanical properties. The mechanical properties and chemical composition of the teeth of extant reptiles are still poorly studied areas. As a preliminary study the fangs of four species of snakes and a human tooth were investigated through nanoindentation and Raman spectroscopy. The average elastic modulus values for the main body of the fangs ranged from 15.3 GPa to 24.6 GPa, and 19.1 GPa for the human dentine. Raman spectroscopy and principal component analysis (PCA) showed that snake fangs are similar in composition to human dentine, both of which comprised of hydroxyapatite and an organic matrix. The elastic modulus and hardness data were correlated to the Raman spectra using partial least squares regression (PLS). The spectral features which correlated with the elastic modulus would suggest that elastic modulus is dependent on the relative protein to mineral amounts in the tooth. The form of the phosphate and the relative levels of phosphate to organic components also appear to be governing factors for elastic modulus. The PLS of Raman spectra against the hardness gave very similar results. The small differences between snake fangs and human dentine appeared to be because of carbonate content, with higher levels of carbonate in the human tooth than the snake fangs. Snake fangs should be able to withstand large lateral forces. Human dentine aids in dissipating imposed loads. This similarity in the chemical composition of the snake fangs and human dentine supported the findings of the similarities in mechanical properties, which may be attributed to the similar functional demands of these biocomposites. Copyright © 2016 John Wiley & Sons, Ltd.     

Near-field scanning optical microscopy: a tool for nanometric exploration of biological membranes

Near-field scanning optical microscopy (NSOM) is an emerging optical technique that enables simultaneous high-resolution fluorescence and topography measurements. Here we discuss selected applications of NSOM to biological systems that help illustrate the utility of its high spatial resolution and simultaneous collection of both fluorescence and topography. For the biological sciences, these attributes seem particularly well suited for addressing ongoing issues in membrane organization, such as those regarding lipid rafts, and protein–protein interactions. Here we highlight a few NSOM measurements on model membranes, isolated biological membranes, and cultured cells that help illustrate some of these capabilities. We finish by highlighting nontraditional applications of NSOM that take advantage of the small probe to create nanometric sensors or new modes of imaging.     

Vault ribonucleoprotein particles and the central mass of the nuclear pore complex

Nuclear pore complexes (NPCs) are macromolecular pores that span the nuclear envelope and undergo conformational changes in response to changes in cisternal calcium levels. Depletion of cisternal calcium leads to the appearance of a mass within the pore. The identity and role of this central mass remain unknown, although some studies suggest they are vault complexes. Vault complexes are 13 MDa ribonucleoproteins found in the cytoplasm and recently in the nuclei of some species, suggesting that they associate with NPCs to cross the nuclear envelope. Using Förster resonance energy transfer (FRET) measurements between labeled vaults and NPCs, we find significant energy transfer suggesting that vaults and NPCs are closely associated at the nuclear envelope. This is supported by high‐resolution electron microscopy measurements revealing significant spatial correlations between gold‐labeled vaults and NPCs. As the location of the central mass in the NPC is dependent on cisternal calcium levels, FRET signals under conditions of varying cisternal calcium were also measured and shown to undergo significant changes. Together, these findings suggest that the central mass observed in NPCs may be, at least in part, due to the presence of vaults in the pore. Possible roles in cyto‐nuclear trafficking are discussed.     

Solvents from biorenewable sources: ionic liquids based on fructose

[reaction: see text] Fructose has been used as the starting material for the preparation of a new class of room-temperature ionic liquids (RTILs). These liquids exhibit tunable solvent properties much like conventional imidazole-based RTILs. They have been applied as recyclable solvents for the Heck reaction of aryl iodides.     

QED effects in molecules: test on rotational quantum states of H2

Quantum electrodynamic effects have been systematically tested in the progression of rotational quantum states in the X?1Σ(g)(+), v=0 vibronic ground state of molecular hydrogen. High-precision Doppler-free spectroscopy of the EF?1Σ(g)(+)-X?1Σ(g)(+) (0,0) band was performed with 0.005 cm(-1) accuracy on rotationally hot H2 (with rotational quantum states J up to 16). QED and relativistic contributions to rotational level energies as high as 0.13 cm(-1) are extracted, and are in perfect agreement with recent calculations of QED and high-order relativistic effects for the H2 ground state.