Activation of phospholipase A2 by Hsp70 in vitro

Corrigendum to “Activation of phospholipase A2 by Hsp70 in vitro” Biochimica et Biophysica Acta (BBA) – Biomembranes Vol. 1838, Issue 7, July 2014, Pages 1921 10.1016/j.bbamem.2014.03.020Peer reviewe

The ultraviolet colour of globular clusters in M31: a core density effect?

We investigate the effect of stellar density on the ultraviolet (UV) emission from M31's globular clusters (GCs). Published far-UV (FUV) and near-UV (NUV) colours from Galaxy Evolution and Explorer (GALEX) observations are used as a probe into the temperature of the horizontal branch (HB) stars in these clusters. From these data, we demonstrate a significant relationship between the core density of a cluster and its FUV-NUV colour, with dense clusters having bluer ultraviolet colours. These results are consistent with a population of (FUV bright) extreme-HB (EHB) stars, the production of which is related to the stellar density in the clusters. Such a relationship may be expected if the formation of EHB stars is enhanced in dense clusters due to dynamical interactions. We also consider the contribution of low mass X-ray binaries (LMXBs) to the integrated FUV luminosity of a cluster. We note that two of the three metal rich clusters, identified by Rey et al. 2007 as having a FUV excess, are known to host LMXBs in outburst. Considering the FUV luminosity of Galactic LMXBs, we suggest that a single LMXB is unlikely to produce more than 10% of the observed FUV luminosity of clusters that contain a significant population of blue-HB stars.Comment: Accepted for publication in MNRAS, 9 pages, 6 figures and 1 tabl

A review of methods for assessment of the rate of gastric emptying in the dog and cat: 1898-2002

Gastric emptying is the process by which food is delivered to the small intestine at a rate and in a form that optimizes intestinal absorption of nutrients. The rate of gastric emptying is subject to alteration by physiological, pharmacological, and pathological conditions. Gastric emptying of solids is of greater clinical significance because disordered gastric emptying rarely is detectable in the liquid phase. Imaging techniques have the disadvantage of requiring restraint of the animal and access to expensive equipment. Radiographic methods require administration of test meals that are not similar to food. Scintigraphy is the gold standard method for assessment of gastric emptying but requires administration of a radioisotope. Magnetic resonance imaging has not yet been applied for assessment of gastric emptying in small animals. Ultrasonography is a potentially useful, but subjective, method for assessment of gastric emptying in dogs. Gastric tracer methods require insertion of gastric or intestinal cannulae and are rarely applied outside of the research laboratory. The paracetamol absorption test has been applied for assessment of liquid phase gastric emptying in the dog, but requires IV cannulation. The gastric emptying breath test is a noninvasive method for assessment of gastric emptying that has been applied in dogs and cats. This method can be carried out away from the veterinary hospital, but the effects of physiological and pathological abnormalities on the test are not known. Advances in technology will facilitate the development of reliable methods for assessment of gastric emptying in small animals

PLA2 Interfacial Activation on Lipid Interfaces Promoting Fibril Formation

Phospholipase A2 is a widely studied protein found ubiquitously in nature. The protein interacts with the lipid membrane cleaving the phospholipid at the sn-2 position. The interfacial activation mechanism is characterized by a low activity on monomeric substrates but a greatly enhanced activity on aggregated substrates. Several of our papers have elucidated the complex interfacial activation mechanism of this protein from different angles in two very diverse scientific frames: from the view of the lipid and the view of the protein. In this thesis the interfacial activation mechanism of PLA2 is understood to behave in a temporal sequence of events first by binding, dimer formation, oligomer formation and finally by the formation of amyloid-like fibrils

Synthesis of polydiacetylene (PDA) particles for detection of histamine

Histamine poisoning as a problem of public health and safety attracted attention worldwide. There is a significant need for devices that are capable of measuring histamine levels rapidly with high sensitivity. In this study, a colorimetric sensor based on polydiacetylene (PDA) was developed for histamine detection. Under optimal conditions, the biosensor showed a linear response to different concentrations of histamine within the range of 21 ppm to 210 ppm with a low detection limit of 10.1 ppm. Moreover, the biosensor was successfully employed to detect the histamine level in the spiked canned fish sample. With high sensitivity and recovery values, this assay can be used to monitor the quality of canned fish, suggesting that it holds great potential for on-site detection and real-time monitoring

ANALYTICAL DETERMINATION OF CORTISOL USING A FLUORESCENT APTAMER ASSAY

Cortisol is a steroid hormone that stimulates gluconeogenesis. A high cortisol concentration in saliva can be an indication of stress and a low concentration can indicate metabolic problems. By monitoring the level of cortisol one can determine and perhaps mitigate their stress levels. Aptamers or chemical antibodies are DNA or RNA sequences (10-100 nucleic acids) that are made synthetically and selected to bind to cells, proteins and small molecules. These molecules can have similar or better affinity and specificity compared to antibodies and are widely used in diagnostics. Since aptamers are composed of nucleotides it is possible to use specific fluorescent tags and intercalating dyes. Here we developed a sensor for detecting cortisol using an aptamer specific for cortisol and a forced intercalating probe (FIT) composed of thiazole orange (TO). The aptamer was saturated with TO and the decrease in fluorescent intensity was measured as a result of the aptamer binding to cortisol. The samples were measured in Tris buffer and in an artificial saliva matrix. The present results demonstrate an inexpensive, yet sensitive technique to measure cortisol in saliva

Activation of phospholipase A2 by temporin B: Formation of antimicrobial peptide-enzyme amyloid-type cofibrils

Phospholipases A2 have been shown to be activated in a concentration dependent manner by a number of antimicrobial peptides, including melittin, magainin 2, indolicidin, and temporins B and L. Here we used fluorescently labelled bee venom PLA2 (PLA2D) and the saturated phospholipid substrate 1,2-dipalmitoyl-glycero-sn-3-phosphocholine (L-DPPC), exhibiting a lag-burst behaviour upon the initiation of the hydrolytic reaction by PLA2. Increasing concentrations of Cys-temporin B and its fluorescent Texas red derivative (TRC-temB) caused progressive shortening of the lag period. TRC-temB/PLA2D interaction was observed by Förster resonance energy transfer (FRET), with maximum efficiency coinciding with the burst in hydrolysis. Subsequently, supramolecular structures became visible by microscopy, revealing amyloid-like fibrils composed of both the activating peptide and PLA2. Reaction products, palmitic acid and 1-palmitoyl-2-lyso-glycero-sn-3-phosphocholine (lysoPC, both at > 8 mol%) were required for FRET when using the non-hydrolysable substrate enantiomer 2,3-dipalmitoyl-glycero-sn-1-phosphocholine (D-DPPC). A novel mechanism of PLA2 activation by co-fibril formation and associated conformational changes is suggeste