Use Of Electron Spin Resonance Spectroscopy Research Articles

Development of a scanning tunneling microscope for variable temperature electron spin resonance.

Recent advances in improving the spectroscopic energy resolution in scanning tunneling microscopy (STM) have been achieved by integrating electron spin resonance (ESR) with STM. Here, we demonstrate the design and performance of a homebuilt STM capable of ESR at temperatures ranging from 1 to 10K. The STM is incorporated with a homebuilt Joule-Thomson refrigerator and a two-axis vector magnet. Our STM design allows for the deposition of atoms and molecules directly into the cold STM, eliminating the need to extract the sample for deposition. In addition, we adopt two methods to apply radio-frequency (RF) voltages to the tunnel junction: the early design of wiring to the STM tip directly and a more recent idea to use an RF antenna. Direct comparisons of ESR results measured using the two methods and simulations of electric field distribution around the tunnel junction show that, despite their different designs and capacitive coupling to the tunnel junction, there is no discernible difference in the driving and detection of ESR. Furthermore, at a magnetic field of ∼1.6T, we observe ESR signals (near 40GHz) sustained up to 10K, which is the highest temperature for ESR-STM measurement reported to date, to the best of our knowledge. Although the ESR intensity exponentially decreases with increasing temperature, our ESR-STM system with low noise at the tunnel junction allows us to measure weak ESR signals with intensities of a few fA. Our new design of an ESR-STM system, which is operational in a large frequency and temperature range, can broaden the use of ESR spectroscopy in STM and enable the simple modification of existing STM systems, which will hopefully accelerate a generalized use of ESR-STM.

The use of ESR spectroscopy for the identification and dose assessment of irradiated pink shrimp (Parapenaeus longirostris) from Turkey

Turkish pink shrimp (Parapenaeus longirostris) samples were studied by electron spin resonance (ESR) spectroscopy for identification and dose assessment purposes. In this work, the calcified shells of shrimps were used as a sample material. Before irradiation, all shrimp shell samples exhibit one weak ESR singlet with a g-factor of 2.0047. After irradiation, all samples exhibit two asymmetric ESR signal components centered at g-values of 2.0013 and 1.9959. The dose–response curves of the samples exposed to gamma radiations were found to be described well by a single saturation exponential function. Variation of ESR signal intensity of irradiated samples at room and−20 °C temperatures with time in a long-term showed that free radicals responsible from the ESR spectrum of shrimp shells were not stable but still detectable after 87 days. Also, the kinetic behavior of signal at g=2.0013 was studied and the additive dose method was used to evaluate the dose in the product.

Applications of Electron Spin Resonance and Spin Trapping in Tropical Parasitic Diseases

Free radicals may be reaction intermediates in biological systems in more situations than are presently recognized. However, progress in detecting such species by Electron Spin Resonance (ESR) has been relatively slow. ESR is a very sensitive technique for free radical detection and characterization. It can be used to investigate very low concentrations of radicals provided that they are stable enough for their presence to be detected. For unstable radicals special techniques have to be employed. One of these methods is called Spin Trapping. Parasitic diseases in tropical and subtropical areas constitute a major health and economic problem. The range of antiparasitic drugs varies widely in structural complexity and action at the subcellular and molecular levels. However, a number of these drugs are thought to exert their action by generating free radicals. Most of the free radical producing drugs used against parasites are: quinones, naphtoquinones, quinone-imines, aminoquinolines, N-oxides and nitroheterocyclic compounds. This review summarizes some of the more relevant achievements of ESR and Spin Trapping applications in parasitic diseases studies. The use of ESR spectroscopy to obtain relevant information about free radical characterization and the analysis of the mechanisms of action of drugs involved in several parasitic diseases is also presented.

The use of ESR spectroscopy for the investigation of dosimetric properties of egg shells

Electron spin resonance (ESR) spectroscopy was used to investigate the dosimetric properties of chicken egg shells. The ESR spectra of the irradiated egg shell were found to have an asymmetric absorption characterized by a major resonance at g ⊥=2.0019 and a minor resonance at g ||=1.9980. The study was carried out on g ⊥=2.0019 signal because of the accuracy of measurements and the possibility of using it as ESR dosimeter. The activation energy ( E), frequency factor ( k 0) and mean-life ( τ) were calculated to be 1.50±0.10 eV, 2×10 13 s −1 and (4.4±0.4)×10 4 year respectively. Dose–response was investigated between dose ranges of 1 Gy and 10 kGy for 60Co γ-rays. Dose–response was found to be appropriate for dosimetry in the range 3 Gy to 10 kGy. The lower limit of observable doses for egg shell sample was about 3 Gy. The other ESR dosimetric parameters of egg shell samples, fading characteristic, light effect, dose-rate dependence and energy dependence, have also been studied in detail. Apart from its non-tissue equivalence, egg shell has very good dosimetric properties with insignificant fading, light independence, linearity in dose–response (3 Gy–10 kGy), dose-rate independence and independence from energy above 500 keV. It suggests that egg shell may be used as a retrospective γ radiation dosimetry after nuclear accidents or other short accidental radiation events.

Use of ESR spectroscopy for the detection of irradiated Crustacea

AbstractFrozen whole tail sections of pink shrimp (Pandalus montagui), tiger prawn (Penaeus monodon), king prawn (Penaeus plebejus) and Mediterranean crevette (Palaemon serratus) were defrosted overnight and either irradiated the following day with doses of 1, 3 and 5 kGy or left unirradiated. Following irradiation the samples were stored for 0, 7,14 or 21 days at 1°C after which the cuticle was removed, freeze‐dried and ground prior to derivation of the electron spin resonance (ESR) spectra. The shape of the ESR signals derived from the irradiated cuticle of the four species were not identical. Subtraction of an average control spectrum from each species from that induced in the corresponding irradiated samples resulted in the isolation of a number of free radical peaks, the heights of which were measured and the sum of the values used as a measure of signal intensity. Both the irradiation dose and length of storage had a highly significant effect on signal intensity. The signal derived from the cuticle of the Mediterranean crevette was the most stable. The isolated radiation‐induced signals from all four species given 3 and 5 kGy were detectable in samples stored at 1°C for at last 14 days.

ESR Studies of Gluten-Lipid Systems

Gluten samples were extracted with chloroform and/or non-ionic detergent solution. The lipid content and the relative proportions of non-storage proteins were determined. Electron spin resonance (ESR) was used to compare the glutens. In control gluten, 2,2,6,6-tetramethylpiperidinooxyl (TEMPO) was observed to be partitioned into two populations, one located in the lipid phase and the other in the protein-water matrix. In Triton X-114 extracted gluten, there was no visible lipid phase, whilst the proportion of TEMPO solubilised in the lipid phase was only reduced by chloroform treatment. Other probes had no affinity for the lipid phase. Spin labelling of cysteine residues showed the presence of at least two nitroxide populations differing in mobility. The detergent extracted samples seemed to have a higher proportion of mobile nitroxide radicals, which could be attributed to the decrease in non-storage proteins. Labelling of lysine residues gave powder-type spectra reflecting an exceptionally rigid environment. These results show the potential use of ESR spectroscopy to obtain a better understanding of the functionality of specific proteins in the development of the gluten network.

Electron spin resonance technique for investigating reactions of free radicals with compounds of biological interest: nucleic acid constituents.

EARLIER, Ingalls and Wall1,2 reported the use of electron-spin resonance spectroscopy to investigate the reactions of hydrogen and other gaseous free radicals with polymers in a finely divided fluff state. Such fluffs are highly accessible to gaseous free radicals, and react readily to produce polymer radicals which are stabilized by their immobility and separation from one another. Consequently, during exposure to a stream of gaseous atoms, easily observable numbers of polymer radicals rapidly accumulate. A limitation of this technique is that only high-molecular weight materials can be prepared as fluffs. This communication describes a general method of radical stabilization which permits investigation of materials of low molecular weight, and discusses spectra illustrating their application.