Inactivation of V79 cells by low-energy protons, deuterons and helium-3 ions

Previous work by ourselves and by others has demonstrated that protons with a linear energy transfer (LET) about 30 V mu m(-1) are more effective at killing cells than doubly charged particles of the same LET. In this work we show that by using deuterons, which have about twice the range of protons with the same LET, it is possible to extend measurements of the RBE of singly charged particles to higher LET (up to 50 keV mu m(-1)). We report the design and use of a new arrangement for irradiating V79 mammalian cells. Cell survival. measurements have been made using protons in the energy range 1.0-3.7 MeV, deuterons in the energy range 0.9-3.4 MeV and He-3(2+) ions in the energy range 3.4-6.9 MeV;. This corresponds to volume-averaged LET (within the cell nucleus) between 10 and 28 keV mu m(-1) for protons, 18-50 keV mu m(-1) for deuterons, and 59-106 keV mu m(-1) for helium ions. Our results show no difference in the effectiveness of protons and deuterons matched for LET. However, for LET above about 30 keV mu m(-1) singly charged particles are more effective at inactivating cells than doubly-charged particles of the same LET and that this difference can be understood in terms of the radial dose distribution around the primary ion track.

Au Nanoparticles for Applications in Analysis of Cellular and Biomolecular Recognitions

Au nanoparticles (AuNPs) have attracted a great interest in fabrication of various biosensor systems for analysis of cellular and biomolecular recognitions. In conjunction with vast conjugation chemistry available, the materials are easily coupled with biomolecules such as nucleic acids, antigens or antibodies in order to achieve their many potential applications as ligand carriers or transducing platforms for preparation, detection and quantification purposes. Furthermore, the nanoparticles possess easily tuned and unique optical/ physical/ chemical characteristics, and high surface areas, making them ideal candidates to this end. In this topic, sensing mechanisms based on localized surface plasmon resonance (LSPR), particle aggregation, catalytic property, and Fluorescence Resonance Energy Transfer (FRET) of AuNPs as well as barcoding technologies including DNA biobarcodes will be discussed.

The role of LL-37 in periodontal wound healing

Introduction: As a result of chronic inflammation during periodontal disease the junctional epithelium becomes micro-ulcerated. The inflammatory process is mediated by both bacterial and host cell products. Host defence peptides such as defensins, secretory leucocyte protease inhibitor (SLPI) and the sole human cathelicidin, LL-37, are secreted by both periodontal cells and neutrophils into gingival crevicular fluid (GCF). They have the ability to modulate the immune response in periodontitis and are thought to have a potential role in periodontal wound healing. Objectives: The aims of this study were to determine the role of LL-37 in the production of Interleukin (IL)-8, IL-6, hepatocyte growth factor (HGF) and basic-fibroblast growth factor (bFGF) by gingival fibroblasts. The role of LL-37 in modulating total matrix metalloproteinase (MMP) activity and expression of tissue inhibitors of metalloproteinase (TIMP)-1 and -2 by gingival fibroblasts was also investigated. Methods: Primary gingival fibroblasts were co-cultured with concentrations of LL-37 (1, 5 and 10µg/ml) for 24 hours and their supernatants tested for levels of IL-8 and IL-6, HGF, bFGF, TIMP-1 and TIMP-2 by ELISA. Rates of MMP turnover in the supernatants were tested by fluorogenic assay using fluorescence resonance energy transfer (FRET) peptide substrates. Cytotoxicity was measured by MTT assay. Statistical significance was measured using the independent t-test and p<0.05 was considered significant. Results: LL-37 significantly upregulated levels of IL-8, IL-6, HGF, bFGF and TIMP-1 (p<0.05) in a dose-dependent fashion. LL-37 significantly decreased the total MMP activity (p<0.05). None of the LL-37 concentrations tested were cytotoxic to gingival fibroblasts. Conclusion: These results indicate that LL-37 is involved in periodontal wound healing. LL-37 increased levels of proinflammatory cytokines and increased levels of growth factors involved in re-epithelialisation. LL-37 has the ability to regulate remodelling of the periodontium by controlling MMP overactivity both directly and by stimulating production of inhibitors by gingival fibroblasts.

Specific Noncompetitive Immunoassay for HT-2 Mycotoxin Detection

Here we demonstrate a novel homogeneous one-step immunoassay, utilizing a pair of recombinant antibody antigen-binding fragments (Fab), that is specific for HT-2 toxin and has a positive readout. Advantages over the conventional competitive immunoassay formats such as enzyme-linked immunosorbent assay (ELISA) are the specificity, speed, and simplicity of the assay. Recombinant antibody HT2-10 Fab recognizing both HT-2 and T-2 toxins was developed from a phage display antibody library containing 6 × 10(7) different antibody clones. Specificity of the immunoassay was introduced by an anti-immune complex (IC) antibody binding the primary antibody-HT-2 toxin complex. When the noncompetitive immune complex assay was compared to the traditional competitive assay, an over 10-fold improvement in sensitivity was observed. Although the HT2-10 antibody has 100% cross-reactivity for HT-2 and T-2 toxins, the immune complex assay is highly specific for HT-2 alone. The assay performance with real samples was evaluated using naturally contaminated wheat reference material. The half-maximal effective concentration (EC50) value of the time-resolved fluorescence resonance energy transfer (TR-FRET) assay was 9.6 ng/mL, and the limit of detection (LOD) was 0.38 ng/mL (19 μg/kg). The labeled antibodies can be predried to the assay vials, e.g., microtiter plate wells, and readout is ready in 10 min after the sample application.

RF energy harvesting two-way cognitive DF relaying with transceiver impairments

This paper analyzes the impact of transceiver impairments on outage probability (OP) and throughput of decode-and-forward two-way cognitive relay (TWCR) networks, where the relay is self-powered by harvesting energy from the transmitted signals. We consider two bidirectional relaying protocols namely, multiple access broadcast (MABC) protocol and time division broadcast (TDBC) protocol, as well as, two power transfer policies namely, dual-source (DS) energy transfer and single-fixed-source (SFS) energy transfer. Closed-form expressions for OP and throughput of the network are derived in the context of delay-limited transmission. Numerical results corroborate our analysis, thereby we can quantify the degradation of OP and throughput of TWCR networks due to transceiver hardware impairments. Under the specific parameters, our results indicate that the MABC protocol achieves asymptotically a higher throughput by 0.65 [bits/s/Hz] than the TDBC protocol, while the DS energy transfer scheme offers better performance than the SFS policy for both relaying protocols.

Amyloid B-peptide 1-40 increases neuronal membrane fluidity: role of cholesterol and brain region

There is increasing evidence of an interaction between cholesterol dynamics and Alzheimer's disease (AD), and amyloid ß-peptide may play an important role in this interaction. Aß destabilizes brain membranes and this action of Aß may be dependent on the amount of membrane cholesterol. We tested this hypothesis by examining effects of Aß1-40 on the annular fluidity (i.e., lipid environment adjacent to proteins) and bulk fluidity of rat synaptic plasma membranes (SPM) of the cerebral cortex, cerebellum, and hippocampus using the fluorescent probe pyrene and energy transfer. Amounts of cholesterol and phospholipid of SPM from each brain region were determined. SPM of the cerebellum were significantly more fluid as compared with SPM of the cerebral cortex and hippocampus. Aß significantly increased (P 0.01) annular and bulk fluidity in SPM of cerebral cortex and hippocampus. In contrast, Aß had no effect on annular fluidity and bulk fluidity of SPM of cerebellum. The amounts of cholesterol in SPM of cerebral cortex and hippocampus were significantly higher (P 0.05) than amount of cholesterol in SPM of cerebellum. There was significantly less (P 0.05) total phospholipid in cerebellar SPM as compared with SPM of cerebral cortex. Neuronal membranes enriched in cholesterol may promote accumulation of Aß by hydrophobic interaction, and such an interpretation is consistent with recent studies showing that soluble Aß can act as a seed for fibrillogenesis in the presence of cholesterol.

Vortex shedding and drag in dilute Bose-Einstein condensates

Above a critical velocity, the dominant mechanism of energy transfer between a moving object and a dilute Bose-Einstein condensate is vortex formation. In this paper, we discuss the critical velocity for vortex formation and the link between vortex shedding and drag in both homogeneous and inhomogeneous condensates. We find that at supersonic velocities sound radiation also contributes significantly to the drag force.

Dissipation and vortex creation in Bose-Einstein condensed gases

We solve the Gross-Pitaevskii equation to study energy transfer from an oscillating

A review of dsb induction data for varying quality radiations

Purpose: This short review summarizes the data obtained with various techniques for measuring the yields of double strand breaks (dsb) produced by particle radiations of differing linear energy transfer (LET) in order to obtain relative biological effectiveness (RBE) values.

A study of endonuclease III-sensitive sites in irradiated DNA: detection of alpha-particle-induced oxidative damage

An important difference between chemical agents that induce oxidative damage in DNA and ionizing radiation is that radiation-induced damage is clustered locally on the DNA, Both modelling and experimental studies have predicted the importance of clustering of lesions induced by ionizing radiation and its dependence on radiation quality. With increasing linear energy transfer, it is predicted that complex lesions will be formed within 1-20 bp regions of the DNA, As well as strand breaks, these sites may contain multiple damaged bases, We have compared the yields of single strand breaks (ssb) and double strand breaks (dsb) along with those produced by treatment of irradiated DNA with the enzyme endonuclease III, which recognizes a number of oxidized pyrimidines in DNA and converts them to strand breaks. Plasmid DNA was irradiated under two different scavenging conditions to test the involvement of OH radicals with either Co-60 gamma-rays or alpha-particles from a Pu-238 source. Under low scavenging conditions (10 mM Tris) gamma-irradiation induced 7.1x10(-7) ssb Gy/bp, which increased 3.7-fold to 2.6 x 10(-6) ssb Gy/bp with endo III treatment. In contrast the yields of dsb increased by 4.2-fold from 1.5 x 10(-8) to 6.3 x 10(-8) dsb Gy/bp, This equates to an additional 2.5% of the endo III-sensitive sites being converted to dsb on enzyme treatment. For alpha-particles this increased to 9%. Given that endo III sensitive sites may only constitute similar to 40% of the base lesions induced in DNA, this suggests that up to 6% of the ssb measured in X- and 22% in alpha-particle-irradiated DNA could have damaged bases associated with them contributing to lesion complexity.

Ubiquitous Nature of Multimode Vibrational Resonances in Positron-Molecule Annihilation

Positron annihilation on many molecules occurs via positron capture into vibrational Feshbach resonances, with annihilation rates often further enhanced by energy transfer to vibrational excitations weakly coupled to the positron continuum. Data presented here uncover another scenario in which the positron couples directly to a quasicontinuum of multimode vibrational states. A model that assumes excitation and escape from a statistically complete ensemble of multimode vibrations is presented that reproduces key features of the data.

Co-operating retrodirective system

Practical demonstration of the operational advantages gained through the use of a co-operating retrodirective array (RDA) basestation and Van Atta node arrangements is discussed. The system exploits a number of inherent RDA features to provide analogue real time multifunctional operation at low physical complexity. An active dual-conversion four element RDA is used as the power distribution source (basestation) while simultaneously achieving a receive sensitivity level of ??109 dBm and 3 dB automatic beam steering angle of ??45??. When mobile units are each equipped with a semi-passive four element Van Atta array, it is shown mobile device orientation issues are mitigated and optimal energy transfer can occur because of automatic beam formation resulting from retrodirective self-pointing action. We show that operation in multipath rich environments with or without line of sight acts to reduce average power density limits in the operating volume with high energy density occurring at mobile nodes sites only. The system described can be used as a full duplex ASK communications link, or, as a means for remote node charging by wireless means, thereby enhancing deployment opportunities between unstabilised moving platforms.

Relative Biological Effectiveness Variation Along Monoenergetic and Modulated Bragg Peaks of a 62-MeV Therapeutic Proton Beam: A Preclinical Assessment

iological optimization of proton therapy critically depends on detailed evaluation of relative biological effectiveness (RBE) variations along the Bragg curve. The clinically accepted RBE value of 1.1 is an oversimplification, which disregards the steep rise of linear energy transfer (LET) at the distal end of the spread-out Bragg peak. We observed significant cell killing RBE variations dependent on beam modulation, intrinsic radiosensitivity, and LET in agreement with the LEM predicted values, indicating dose-averaged LET as a suitable parameter for biological effectiveness. Data have also been used to validate a RBE parameterized model.

Demonstration of laser pulse amplication by stimulated Brillouin scattering

The energy transfer by stimulated Brillouin backscatter from a long pump pulse (15 ps) to a short seed pulse (1 ps)has been investigated in a proof-of-principle demonstration experiment. The two pulses were both amplified in differentbeamlines of a Nd:glass laser system, had a central wavelength of 1054 nm and a spectral bandwidth of 2 nm, and crossedeach other in an underdense plasma in a counter-propagating geometry, off-set by 10◦. It is shown that the energy transferand the wavelength of the generated Brillouin peak depend on the plasma density, the intensity of the laser pulses, and thecompetition between two-plasmon decay and stimulated Raman scatter instabilities. The highest obtained energy transferfrom pump to probe pulse is 2.5%, at a plasma density of 0.17ncr, and this energy transfer increases significantly withplasma density. Therefore, our results suggest that much higher efficiencies can be obtained when higher densities (above0.25ncr) are used.

(223)Ra and other bone-targeting radiopharmaceuticals-the translation of radiation biology into clinical practice

Osseous metastases are a source of significant morbidity for patients with a variety of cancers. Radiotherapy is well established as an effective means of palliating symptoms associated with such metastases. The role of external beam radiotherapy is limited where sites of metastases are numerous and widespread. Low linear energy transfer (LET) radionuclides have been utilized to allow targeted delivery of radiotherapy to disparate sites of disease, with evidence of palliative benefit. More recently, the bone targeting, high LET radionuclide (223)Ra has been shown to not only have a palliative effect but also a survival prolonging effect in metastatic, castration-resistant prostate cancer with bone metastases. This article reviews the different radionuclide-based approaches for targeting bone metastases, with an emphasis on (223)Ra, and key elements of the underlying radiobiology of these that will impact their clinical effectiveness. Consideration is given to the remaining unknowns of both the basic radiobiological and applied clinical effects of (223)Ra as targets for future research.