Free radical and overtone spectroscopy

In the fall of 1987 during a photoacoustic study of hydrogen peroxide's fourth vibrational overtone band, the remarkably clear and well resolved spectrum was observed. Its periodicity and K subband structure suggested that the spectrum was not of hydrogen peroxide but of a smaller near-prolate symmetric top molecule. Furthermore, the time dependent behavior of the signal indicated that chemical changes were taking place within the photoacoustic apparatus

Single crystal and supported nano-cluster copper-palladium/platinum model catalysts

This work involved the experimental investigation of a variety of model copperpalladium/ platinum heterogeneous catalysts in the form of single-crystal surfaces (Cu(110)/Pd and Cu(100)/Pt) and highly orientated pyrolytic graphite (HOPG) supported nano-clusters. The surface structural arrangement was primarily examined using scanning tunnelling microscopy (STM) and low energy electron diffraction (LEED) while X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) were used to determine surface composition. In addition, temperature-programmed desorption (TPD) has been employed to probe the reactivity of the surfaces via the decomposition of formic acid (HCOOH). In the case of the Cu(l 10)/Pd system XPS measurements backed up by STM/LEED clearly demonstrate the formation of regions of a Cu(l 10)-p(2xl)-Pd surface alloy at low Pd coverages (0pd<l ML) with considerable disorder in the form of monolayer deep pits and islands. Higher Pd coverages led to the formation of a granular film of epitaxial densely packed flat topped Pd clusters with largely a rectangular shape of average size 75x150 A. The favoured growth mechanism is of multilayered Pd islands above a mixed (2x1) CuPd interface of two to three atomic layers thickness. Only after annealing to 600 K is the granular structure of the higher coverage Pd films disrupted due to inter-diffusion into the Cu substrate, leading to a surface with irregularly shaped flat domains separated by mono-atomic steps. Higher temperature (720 K) annealing led to further flattening and the appearance of regular parallel lines in STM images whose spacing varies with Pd loading, which is assigned to strain due to lattice mismatch between a “capping” outermost copper monolayer and the underlying mixed CuPd alloy. High Pd coverage samples annealed to 500 K displayed substantial destabilisation of the formate intermediate relative to clean Cu(l 10), attributed to formate adsorption on mixed CuPd sites. The nucleation and growth of both monometallic and bimetallic Pd and Cu clusters on HOPG have been investigated. STM, and XPS measurements of monometallic films of Cu and Pd verified a Volmer-Weber growth mechanism with formation of hemispherical monometallic clusters of average diameter ~4 nm (Pd) and ~8 nm (Cu). Bimetallic films of Cu and Pd formed by sequential deposition revealed properties dependent on the sequence of metal deposition. In the case of Cu deposition on predeposited Pd clusters, preferential coating of Pd by a Cu thin film (themodynamically favourable in surface energy terms) at low Cu coverages is observed, followed by the formation of phase separated Cu clusters as the Cu coverage is increased. XPS measurements rule out substantial alloy formation. STM indicates the majority of hemispherical bimetallic clusters are 5 to 7 nm in diameter, intermediate in size compared to that found for both monometallic Cu and Pd films. For Pd deposition on pre-deposited Cu, XPS data indicate a growth mechanism whereby the simultaneous growth of Pd clusters on the HOPG surface and the alloying/capping of areas already covered by Cu clusters occurs. Shifts in the Cu 2p core-level to lower binding energies for increased Pd loading on all levels of Cu pre-dosed samples illustrate a strong Pd-Cu interaction and fully supports this theory. Again an intermediate cluster-size distribution was observed by STM. In the course of this work a new simple and reliable method for the absolute calibration of surface coverage was developed, based on the ex-situ analysis of the absolute amount of the metal evaporated using graphite furnace atomic adsorption spectroscopy (GF-AAS). This method is shown to have an absolute sensitivity of better than 0.1 ML. The Cu(100)/Pt bimetallic combination has been examined by LEED, AES and TPD. An underlayer c(2><2) CuPt alloy capped by a Cu monolayer may be formed by deposition of ~0.6 ML Pt followed by thermal activation. In contrast, higher coverages of Pt (1.0-2.5 ML) followed by annealing to 550 K led to a local order c(2x2) CuPt alloy with a mixed CuPt top layer. A top layer CuPt alloy led to a destabilisation of the formate intermediate due to adsorption on a mixed CuPt site although the surface chemistry is still similar to pure Cu(100). The underlayer CuPt c(2x2) also exhibits destabilisation of the formate intermediate but to a lesser extent than the c(2x2) mixed CuPt top layer

Peptide de Novo Sequencing Using 157 nm Photodissociation in a Tandem Time-of-Flight Mass Spectrometer

It has previously been shown that photodissociation of tryptic peptide ions with 157 nm light in a matrix-assisted laser desorption/ionization (MALDI) tandem time-of-flight (TOF) mass spectrometer generates an abundance of x-type ions. A peptide de novo sequencing algorithm has now been developed to interpret these data. By combination of photodissociation and postsource decay (PSD) spectra, the algorithm identifies x-type ions and derives peptide sequences. The confidence of amino acid assignments is evaluated by observing complementary y-, v-, and w-type ions that provide additional constraints to sequence identification. In the analysis of 31 tryptic peptides from 4 model proteins, the algorithm identified 322 (or 90.7%) of the 355 amino acids and made only 3 incorrect assignments. The other 30 amino acids were not identified because specific needed x-type ions were not detected. Based on the observation of v-and w-type ions, 45 of 50 detected leucine and isoleucine residues were successfully distinguished and there was only one mistake. The remaining four residues were not distinguished because the corresponding v-and w-type ions were not detected. These de novo sequencing results translated into successful identification of proteins through homology searches. To evaluate the robustness of the present sequencing approach, a collection of 266 tryptic peptides from 23 model proteins were analyzed and then sequenced. A total of 167 peptides yielded sequence tags of 5 or more residues. In 5 peptides, 1 or 2 residues were incorrectly assigned. Mass spectrometry (MS) is widely used to investigate biological systems following recent advances in both instrumentation and bioinformatics. 1-5 A number of MS-based techniques have been developed to characterize protein constituents in biological samples. 6-8 The two most common protein-identification methods involve tandem mass spectrometry (MS/MS) 9,10 and MALDI peptide mass mapping. [11][12][13] In either case, proteolytic peptides are analyzed by mass spectrometry and proteins are assigned by comparing mass spectrometric data with predicted peptide and fragment masses derived from a protein sequence database. Even though these methods have been successfully applied in numerous experiments, they have several fundamental limitations. Experimental data do not lead to correct protein identifications when there are database errors, genetic mutations, and modifications that occur post-translationally or during sample handling. In addition, some peptide fragmentation spectra contain limited sequence information. As a result, only about 10-20% of spectra typically lead to peptide identifications, although some high-quality experiments do yield as high as 50% identifications. 14,15 Furthermore, organisms without sequenced genomes cannot be studied by database-matching techniques. Finally, protein databases continue to grow in size, so the time it takes to search against them increases exponentially. In light of these limitations, methods that can identify peptides without protein databases are desirable. De novo sequencing methods have been developed to derive peptide sequences from tandem mass spectra without reference to a database. 16 Typically de novo sequencing algorithms identify amino acids using mass differentials between consecutive peaks in tandem mass spectra. Several of these algorithms have been developed to interpret low-energy collisionally induced dissociation (CID) spectra including Sherenga, Lutefisk, PEAKS, DACSIM, EigenMS, PepNovo, NovoHMM, and MSNovo. 1,[17][18][19][20][21][22][23] Most pro-* To whom the correspondence should be addressed. E-mail: [email protected].

Dependence of NO rotational photoionization propensity rules on electron kinetic energy

In order to study the effect of photoelectron kinetic energy on rotational photoionization propensity rules, rotationally resolved laser photoelectron spectra were measured for excitation of specific rovibronic levels in the D 2Sigma+ (3psigma) Rydberg state of NO and their subsequent ionization by radiation at several wavelengths. The measured and calculated ion rotational branching ratios both show a significant dependence on photoelectron energy. Comparison between experimental data and theoretical calculations suggests that a strong DeltaN=0 peak in the spectra is caused by an interaction between particular vibronic levels of the A 2Sigma+ (v=4) and D 2Sigma+ (v=0) Rydberg states

Blind signal separation for convolutive mixing environments using spatial-temporal processing

In this paper we extend the infomax technique [1] for blind signal separation from the instantaneous mixing case to the convolutive mixing case. Separation in the convolutive case requires an unmixing system which uses present and past values of the observation vector, when the mixing system is causal. Thus, in developing an infomax process, both temporal and spatial dependence of the observations must be considered. We propose a stochastic gradient based structure which accomplishes this task. Performance of the proposed method is verified by subjective listening tests and quantitative measurements

Performance of an environmental test to detect Mycobacterium bovis infection in badger social groups

A study by Courtenay and others (2006) demonstrated that the probability of detecting Mycobacterium bovis by PCR in soil samples from the spoil heaps of main badger setts correlated with the prevalence of excretion (infectiousness) of captured badgers belonging to the social group. It has been proposed that such a test could be used to target badger culling to setts containing infectious animals (Anon 2007). This short communication discusses the issues surrounding this concept, with the intention of dispelling any misconceptions among relevant stakeholders (farmers, policy makers and conservationists)

IL-21 receptor expression in human tendinopathy

The pathogenetic mechanisms underlying tendinopathy remain unclear, with much debate as to whether inflammation or degradation has the prominent role. Increasing evidence points toward and early inflammatory infiltrate and associated inflammatory cytokine production in human and animal models of tendon disease. The IL-21/IL-21R axis is a proinflammatory cytokine complex that has been associated with chronic inflammatory diseases including rheumatoid arthritis and inflammatory bowel disease. This project aimed to investigate the role and expression of the cytokine/receptor pair IL-21/IL-21R in human tendinopathy. We found significantly elevated expression of IL-21 receptor message and protein in human tendon samples but found no convincing evidence of the presence of IL-21 at message or protein level. The level of expression of IL-21R message/protein in human tenocytes was significantly up regulated by proinflammatory cytokines (TNFα/IL-1β) in vitro. These findings demonstrate that IL-21R is present in early human tendinopathy mainly expressed by tenocytes and macrophages. Despite a lack of IL-21 expression these data again suggest that early tendinopathy has an inflammatory/cytokine phenotype, which may provide novel translational targets in the treatment of tendinopathy

Novel approaches to diagnosis and management of hereditary transthyretin amyloidosis

© Author(s) (or their employer(s)) 2022. Open access This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0Hereditary transthyretin amyloidosis (ATTRv) is a severe, adult-onset autosomal dominant inherited systemic disease predominantly affecting the peripheral and autonomic nervous system, heart, kidney and the eyes. ATTRv is caused by mutations of the transthyretin (TTR) gene, leading to extracellular deposition of amyloid fibrils in multiple organs including the peripheral nervous system. Typically, the neuropathy associated with ATTRv is characterised by a rapidly progressive and disabling sensorimotor axonal neuropathy with early small-fibre involvement. Carpal tunnel syndrome and cardiac dysfunction frequently coexist as part of the ATTRv phenotype. Although awareness of ATTRv polyneuropathy among neurologists has increased, the rate of misdiagnosis remains high, resulting in significant diagnostic delays and accrued disability. A timely and definitive diagnosis is important, given the emergence of effective therapies which have revolutionised the management of transthyretin amyloidosis. TTR protein stabilisers diflunisal and tafamidis can delay the progression of the disease, if treated early in the course. Additionally, TTR gene silencing medications, patisiran and inotersen, have resulted in up to 80% reduction in TTR production, leading to stabilisation or slight improvement of peripheral neuropathy and cardiac dysfunction, as well as improvement in quality of life and functional outcomes. The considerable therapeutic advances have raised additional challenges, including optimisation of diagnostic techniques and management approaches in ATTRv neuropathy. This review highlights the key advances in the diagnostic techniques, current and emerging management strategies, and biomarker development for disease progression in ATTRv.SV gratefully acknowledges funding support from the National Health and Medical Research Council (NHMRC) of Australia (project grant numbers 510233, 1024915 and 1055778; program grant number 1132524; dementia research team grant number 1095127; and Partnership Project number 1153439) and the Motor Neuron Disease Research Institute of Australia. MCK was supported by a NHMRC Practitioner Fellowship (number 1156093).info:eu-repo/semantics/publishedVersio

Projecting the effect of crop yield increases, dietary change and different price scenarios on land use under two different state security regimes

Peer reviewedPublisher PD

Prepubertal exposure to arsenic(III) suppresses circulating insulin-like growth factor-1 (IGF-1) delaying sexual maturation in female rats

Arsenic (As) is a prevalent environmental toxin readily accessible for human consumption and has been identified as an endocrine disruptor. However, it is not known what impact As has on female sexual maturation. Therefore, in the present study, we investigated the effects of prepubertal exposure on mammary gland development and pubertal onset in female rats. Results showed that prepubertal exposure to 10 mg/kg of arsenite (As(III)) delayed vaginal opening (VO) and prepubertal mammary gland maturation. We determined that As accumulates in the liver, disrupts hepatocyte function and suppresses serum levels of the puberty related hormone insulin-like growth factor 1 (IGF-1) in prepubertal animals. Overall, this is the first study to show that prepubertal exposure to As(III) acts peripherally to suppress circulating levels of IGF-1 resulting in delayed sexual maturation. Furthermore, this study identifies a critical window of increased susceptibility to As(III) that may have a lasting impact on female reproductive function