Dielectric Spectroscopy and Membrane Organisation

The possible bases for field-mediated effects on cellular processes are reflected in the passive electrical properties of biological systems. The historical, present and prospective utility of dielectric spectroscopy in assessing the static and dynamic organisation of biological membranes is reviewed within this context. The basis for the view that the static capacitance of bioraembranes is as great as 1 fiF/cm² is doubted; contributions from the (partially restricted) motions of membrane components, and of double-layer ions, probably contribute to this apparent value in bioraembrane vesicle suspensions. The importance of improving our knowledge of the static electrical capacitance of energy coupling membranes is stressed. Theoretical and experimental procedures for assessing the contribution of rotational and translational motions of membrane components, and of double-layer/membrane interactions, to dielectric spectra in the approximate frequency range 10 to 10⁷ Hz are described. Finally, three outstanding and generally unsolved problems requiring further work are detailed.     

Surface Plasmon-Enhanced Spectroscopy and Photochemistry

A review of selected recent contributions to the area plasmon-enhanced spectroscopy and photochemistry is presented.     

Impedance Spectroscopy Revisited

Impedance spectroscopy has been widely used in characterizing the electronic properties of semiconductors. Its application in the perovskite photovoltaic research is a natural extension of the well‐established methodology in the new semiconducting material. However, it turns out that the published results are sometimes very strange, difficult to interpret, or the interpretations contradict each other. It is now clear that most of these troubles stem from the dominating influence of ionic contributions. Herein, some of the published data are reviewed and the possible problems are identified, which can be reconciled by taking into account the explicit contribution of the ionic behavior.     

荧光相关谱技术及其应用

基于对处于平衡态少量荧光分子集合的强度涨落进行时间平均的技术,荧光相关谱fluoreswceance correlation spectroscopy,FCS)技术最近已经应用于细胞环境过程的研究。FCS优秀的灵敏特性为我们实时测量许多参数提供了途径,而且具有快速的时间特性和高空间分辨率。测量的参数包括扩散速率、局部浓度、聚合状态和分子间的相互作用。荧光互相关谱(fluorescence cross-correlation spectroscopy,FCCS)进一步扩展了FCS技术的应用,包括在活细胞中的广泛应用。本文介绍了FCS技术的原理、实验装置及其应用。     

褪黑素的太赫兹时域光谱

太赫兹时域光谱技术是一种新兴的无损探测技术。利用太赫兹波的低能性以及大部分生物分子的振动跃迁和旋转在该频段表现出的强色散和吸收作用等特点,可以对生物分子及生命体的活动进行无损探测和研究。本文分别采用透射式和反射式太赫兹时域光谱系统,对不同质量比的褪黑素压片进行测试,分析它在太赫兹波段的光学性质,发现它在0.29、0.50、0.70、0.91、1.20、2.17和2.55 THz处存在特征吸收峰;频域谱的强度随样品浓度的变化呈线性关系。利用Gaussian 09及Gaussian VIEW软件进行模拟分析,得到褪黑素在0.46、0.91、1.15、2.01、2.23和2.61 THz处存在特征吸收峰,为实验结果提供了有力地支持。这些工作为褪黑素等生化样品的检测和鉴定提供了依据和参考。     

Photo-Acoustic Spectroscopy of Pubescent Leaves

The optical absorption spectra of pubescent (hairy) and depubescisedleaves of Blumea oxydonta DC and Gomphrena decumbens Jacq weretaken using the relatively new technique of photo-acoustic spectroscopy.The pubescent leaf gave a higher photo-acoustic intensity thanthe depubescised leaf. The adaptive significance of pubescenceto the leaf is discussed. Key words: Photo-acoustic spcctroscopy, pubescence     

Infrared Spectroscopy of Some Mannans

Bacterial production of 4-hydroxy(3,4-d)pyrazolopyrirnidine riboside (AP–R) was studied. Seven among 73 tested strains were found to produce AP–R through N-ribosyl transfer reaction between uridine and 4-hydroxy(3,4-d)pyrazolopyrimidine (allopurinol). AP–R was produced by the cell-free extract of Erwinia carotovora and was isolated in crystals from the reaction mixture. The crystalline AP–R was characterized by spectroscopic data and was confirmed to be β-1-ribosyl allopurinol. AP–R could not substitute for inosine to support the growth of a nonexacting purine base-requiring mutant of Sarcina lutea.     

Spectroscopy of a Thomson atom

An analysis is made of the normal oscillations of three-dimensional configurations of dust grains trapped in a spherically symmetric potential well. The frequencies and polarizations of oscillations of a system consisting of four to six grains are calculated for an arbitrary intergrain interaction potential. The possibility of reconstructing the interaction potential from the experimentally measured coordinates of individual grains is discussed.     

Terahertz Time-Domain Spectroscopy of Glucose and Uric Acid

We report the use ofterahertz time-domain spectroscopy for thestudy of two therapeutic bio-molecules:glucose and uric acid. Terahertztransmission spectra of crystalline samplesof both molecules were measured between 0.1–3.0 THz using an evacuated spectroscopysystem. We propose that the stereo-isomersof glucose show spectral featuresoriginating from intermolecular vibrationalmodes, as do uric acid and its derivativemolecule, allantoin. In addition, wepresent a full temperature dependence ofthe terahertz absorption of L-glucose.     

Raman Spectroscopy of Microbial Pigments

Raman spectroscopy is a rapid nondestructive technique providing spectroscopic and structural information on both organic and inorganic molecular compounds. Extensive applications for the method in the characterization of pigments have been found. Due to the high sensitivity of Raman spectroscopy for the detection of chlorophylls, carotenoids, scytonemin, and a range of other pigments found in the microbial world, it is an excellent technique to monitor the presence of such pigments, both in pure cultures and in environmental samples. Miniaturized portable handheld instruments are available; these instruments can be used to detect pigments in microbiological samples of different types and origins under field conditions.     

氨基酸酯化方法的比较及其红外光谱研究

在合成氨基酸酯锗类化合物时,制备了八种氨基酸酯,对文献提供的六种方法进行了实验比较,选出经济简便、产率高的方法。并对氨基酸及其酯的红外光谱的变化特征进行了研究。     

胆绿素的激光表面增强拉曼光谱研究

本文中 ,SERS被用来测定胆绿素 ,并对溶液中的 p H和 Na Cl浓度对谱图的影响进行了研究。测定下限可达 1 .2 8× 1 0 -7M,且摄谱时间只需 1 5分钟。另外 ,讨论了胆绿素在银胶表面的吸附状态及质子化状态。研究表明胆绿素在银胶表面是呈近乎平面的环状结构吸附 ,其内酰胺环 A上氧原子和吡咯环上的氮原子可能发生了质子化。     

Scanning-probe Single-electron Capacitance Spectroscopy

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the electronic quantum structure of small systems - including individual atomic dopants in semiconductors. Here we present a capacitance-based method, known as Subsurface Charge Accumulation (SCA) imaging, which is capable of resolving single-electron charging while achieving sufficient spatial resolution to image individual atomic dopants. The use of a capacitance technique enables observation of subsurface features, such as dopants buried many nanometers beneath the surface of a semiconductor material^1,2,3. In principle, this technique can be applied to any system to resolve electron motion below an insulating surface.As in other electric-field-sensitive scanned-probe techniques⁴, the lateral spatial resolution of the measurement depends in part on the radius of curvature of the probe tip. Using tips with a small radius of curvature can enable spatial resolution of a few tens of nanometers. This fine spatial resolution allows investigations of small numbers (down to one) of subsurface dopants^1,2. The charge resolution depends greatly on the sensitivity of the charge detection circuitry; using high electron mobility transistors (HEMT) in such circuits at cryogenic temperatures enables a sensitivity of approximately 0.01 electrons/Hz^½ at 0.3 K ⁵.     

Light-induced Difference Terahertz Spectroscopy

Visible/near-infraredlaser-induced difference spectroscopy basedon a time-domain terahertz system has beendeveloped, and used to study copperpathancyonine. We find that the absorptionpeak of this molecule at 1.08 THz changessignificantly under 790 nm laserexcitation, suggesting that we haveobserved the first evidence of vibrationalmode changes in the THz range induced byvisible/near-infrared light.     

Broadband Transmission EPR Spectroscopy

EPR spectroscopy employs a resonator operating at a single microwave frequency and phase-sensitive detection using modulation of the magnetic field. The X-band spectrometer is the general standard with a frequency in the 9–10 GHz range. Most (bio)molecular EPR spectra are determined by a combination of the frequency-dependent electronic Zeeman interaction and a number of frequency-independent interactions, notably, electron spin – nuclear spin interactions and electron spin – electron spin interactions, and unambiguous analysis requires data collection at different frequencies. Extant and long-standing practice is to use a different spectrometer for each frequency. We explore the alternative of replacing the narrow-band source plus single-mode resonator with a continuously tunable microwave source plus a non-resonant coaxial transmission cell in an unmodulated external field. Our source is an arbitrary wave digital signal generator producing an amplitude-modulated sinusoidal microwave in combination with a broadband amplifier for 0.8–2.7 GHz. Theory is developed for coaxial transmission with EPR detection as a function of cell dimensions and materials. We explore examples of a doublet system, a high-spin system, and an integer-spin system. Long, straigth, helical, and helico-toroidal cells are developed and tested with dilute aqueous solutions of spin label hydroxy-tempo. A detection limit of circa 5 µM HO-tempo in water at 800 MHz is obtained for the present setup, and possibilities for future improvement are discussed.     

Photoemission Spectroscopy Characterization of Halide Perovskites

Controlling the surface and interface properties of halide perovskites (HaPs) materials is key to improve performance and stability of HaP‐based optoelectronic devices such as solar cells. Here, an overview is given on the use of different photoemission spectroscopy (PES) techniques as a tool kit to investigate chemical and electronic properties of surfaces and interfaces in research on HaP compounds. The primary focus of the article is X‐ray photoelectron spectroscopy (XPS), hard X‐ray photoemission spectroscopy (HAXPES), ultraviolet photoemission spectroscopy (UPS), and inverse photoemission spectroscopy (IPES), highlighting the importance of good practices during PES measurements. Starting from the working principles of PES, critical measurement conditions are discussed. In particular, the exposure of the HaP surface to vacuum and high energy radiation can cause accelerated ageing, degradation, and also ionic migration in the sample. The impact of these changes on the electronic and chemical properties is discussed, followed by an analysis of the specific challenges encountered when performing PES measurements of HaPs. These include the deviation from pristine surface conditions, determination of “soft” band edges, and assessment of band bending. The review concludes by emphasizing good practices for PES measurements of HaP samples and outlining the scope of operando type measurements to capture the transient behavior of HaPs in the experiment.