Tryptophan-to-dye fluorescence energy transfer applied to oxygen sensing by using type-3 copper proteins

A fluorescence-based system to sense oxygen in solution is described. The method exploits the sensitivity of the endogenous fluorescence of type-3 copper proteins towards the presence of oxygen by translating the near-UV emission of the protein to label fluorescence in the visible range through a FRET mechanism. The main protein in this study, a recombinant tyrosinase from the soil bacterium Streptomyces antibioticus, has been covalently labeled with a variety of fluorescent dye molecules with emission maxima spanning the whole visible wavelength range. In all cases, the emission of the label varied considerably between O2-bound and O2-free protein with a contrast exceeding that of the Trp emission for some labels. It is shown that different constructs may be simultaneously observed using a single excitation wavelength. Next to the described application in oxygen sensing, the method may be applicable to any protein showing variations in tryptophan fluorescence, for example as a function of ligand binding or catalysis.     

HL—1M装置1998年物理实验进展报告

报道了ＨＬ－１Ｍ装置１９９８年度物理实验的进展情况。主要包括等离子体密度极限,中性束注入加热,离子回旋共振加热,低温杂波离子加热,多发弹丸注入,超声分子束注入等实验的情况。     

Astrophysical S-factors from asymptotic normalization coefficients

S-factors for direct capture reactions can be found at astrophysical energies from asymptotic normalization coefficients which provide the normalization of the tail of the overlap function. For example the overlap for ⁸B → ⁷Be+p defines the S-factor for ⁷Be (p, γ)⁸B. Peripheral transfer reactions offer a technique to determine these asymptotic normalization coefficients. As a test of the technique, the ¹⁶O(³He, d)¹⁷F reaction has been used to determine asymptotic normalization coefficients for transitions to the ground and first excited states of ¹⁷F. The S-factors for ¹⁶O(p, γ)¹⁷F calculated from these ¹⁷F → ¹⁶O+p asymptotic normalization coefficients are found to be in very good agreement with recent measurements. Following the same technique, the ¹⁰B(⁷Be, ⁸B)⁹Be and ¹⁴N(⁷Be, ⁸B)¹³C reactions have been used to measure the asymptotic normalization coefficient for ⁷Be(p, γ)⁸B. This result provides an indirect determination of S ₁₇(0).     

A Competitive Stapled Peptide Screen Identifies a Selective Small Molecule that Overcomes MCL-1-Dependent Leukemia Cell Survival

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Highlights? A stapled peptide-based screen identified a selective molecular inhibitor of MCL-1 ? MIM1 targets a subregion of the BH3-binding pocket of antiapoptotic MCL-1 ? In contrast to ABT-737, MIM1 binds and functionally neutralizes MCL-1 but not BCL-X_L ? MIM1 exhibits MCL-1-dependent antileukemia activity and synergizes with ABT-737     

Bi‐Enzyme Sensor for Phenolic Compounds with Fluorescent Read‐Out

In this paper, the use of tyrosinase (Ty) from Streptomyces antibioticus, labeled with a fluorescent tag, in combination with soluble quinoprotein (PQQ‐containing) glucose dehydrogenase (s‐GDH) to measure trace amounts of phenols is explored. Proof of concept is provided by a series of experiments, which show a clear quantitative dependence of the response on the phenol concentration. One of the advantages of the detection system is that apart from a standard fluorimeter no further instrumentation is required.     

Facile and Reliable Emission-Based Nanomolar Anion Sensing by Luminescent Iridium Receptors Featuring Chelating Halogen-Bonding Sites

An anion sensor is presented that combines a bidentate hydrogen- (HB) or halogen-bonding (XB) site with a luminescent monocationic Ir fragment for strong binding of common anions (K_a up to 6×10⁴ m ⁻¹) with diagnostic emission changes. A new emission-based protocol for fast and reliable detection was derived on the basis of correction for systematic but unspecific background effects. Such a simple correction routine circumvents the hitherto practical limitations of systematic emission-based analysis of anion binding with validated open-source software (BindFit). The anticipated order of K_a values was obeyed according to size and basicity of the anions (Cl>Br=OAc) as well as the donor atom of the receptor (XB: 6×10⁴ m ⁻¹ > HB: 5×10³ m ⁻¹), and led to submicromolar limits of detection within minutes. The results were further validated by advanced NMR techniques, and corroborated by X-ray crystallographic data and DFT analysis, which reproduced the structural and electronic features in excellent agreement. The results suggest that corrected emission-based sensing may become a complementary, reliable, and fast tool to promote the use of XB in various application fields, due to the simple and fast optical determination at high dilution.     

Two Mathematically Equivalent Versions of Maxwell’s Equations

This paper is a review of the canonical proper-time approach to relativistic mechanics and classical electrodynamics. The purpose is to provide a physically complete classical background for a new approach to relativistic quantum theory. Here, we first show that there are two versions of Maxwell’s equations. The new version fixes the clock of the field source for all inertial observers. However now, the (natural definition of the effective) speed of light is no longer an invariant for all observers, but depends on the motion of the source. This approach allows us to account for radiation reaction without the Lorentz-Dirac equation, self-energy (divergence), advanced potentials or any assumptions about the structure of the source. The theory provides a new invariance group which, in general, is a nonlinear and nonlocal representation of the Lorentz group. This approach also provides a natural (and unique) definition of simultaneity for all observers.     

中国环流器新一号装置总体联调

本文介绍中国环流器新一号装置工程总体联合调试的内容和主要结果。该装置总体联调是非常成功的，获得了重复性很好，环电流平顶宽的稳定平稳的放电波形，这对物理实验的开展非常有利。     

Pulse rise-time characterization of a high pressure xenon gamma detector for use in resolution enhancement

High pressure xenon ionization chamber detectors are possible alternatives to traditional thallium doped sodium iodide [NaI(Tl)] and hyperpure germanium as gamma-spectrometers in certain applications. Xenon detectors incorporating a Frisch grid exhibit energy resolutions comparable to cadmium/zinc/telluride (CZT) (e.g., 2% @ 662 keV) but with far greater sensitive volumes. The Frisch grid reduces the position dependence of the anode pulse rise-times, but it also increases the detector vibration sensitivity, anode capacitance, voltage requirements and mechanical complexity. We have been investigating the possibility of eliminating the grid electrode in high-pressure xenon detectors and preserving the high energy resolution using electronic rise-time compensation methods. A two-electrode cylindrical high pressure xenon gamma-detector coupled to time-to-amplitude conversion electronics was used to characterize the pulse rise-time of deposited gamma-photons. Time discrimination was used to characterize the pulse rise-time versus photo peak position and resolution. These data were collected to investigate the effect of pulse rise-time compensation on resolution and efficiency.     

Uranyl Soil Extraction and Fluorescence Enhancement by Nanoporous Silica Gel: pH effects

Nanoporous silica gel was employed to extract uranyl from contaminated soil and to enhance the fluorescence intensity and lifetime. The fluorescence lifetime and intensity of uranyl ions absorbed within nanoporous silica gel was measured from pH 1?C13. The results show that the uranyl fluorescence intensity can be enhanced by approximately two orders of magnitude by the silica nanoporous matrix from pH 4?C12 with the greatest enhancement occurring from pH 4?C7. The enhanced fluorescence lifetime can be used in time-gated measurements to help minimize the influence of background environmental fluorophores.