The structure of two alanine containing ferrichromes: Sequence determination by proton magnetic resonance

Summary Metal coordination confers an extraordinary structural stability to the ferrichromes which, independent of their variable amino acid composition, results in a basically unperturbed conformation for all the homologous peptides in the series. The proton magnetic resonance (pmr) characteristics for Al³⁺ analogues (alumichromes) reflect this conformational isomorphism in usual solvents so that single site substitutions are clearly recognized in the pmr spectra. Thus, the substitution of glycine byl-alanine orl-serine introduce new resonances characteristic of the sidechains and alter the pattern of the amide NH pmr region in that doublets substitute for glycyl triplets at the same site. Since for glycine- andl-serine-containing alumichromes the resonances have already been identified, it is possible to unequivocally establish the primary structure of the twol-alanyl homologues ferrichrome C ( ) and sake colorant A ( ) on the basis of the comparative pmr spectra of their Al³⁺ analogues, namely, alumichrome C and alumisake. The resonance assignment, and hence the site occupancy, is substantiated by the temperature coefficients of the NH chemical shifts, rates of¹H-²H exchange and homonuclear proton spin decoupling experiments centered on the NH spectral region. Occupancy of site 1 by a glycine residue is observed for all known ferrichromes, which serves to conserve a hairpin turn. This method of obtaining sequence information should prove of general use for other systems of homologous polypeptides, provided their conformations are not affected by the residue substitutions.     

The identification of cholesterol and other steroids in Euphorbia pulcherimma

The 4-desmethyl tetracycles of the whole poinsettia plant (Euphorbia pulcherimma) less roots amounted to 0.07% of the wet wt and were shown by ¹H NMR spectroscopy to be steroids and not euphoids. The most abundant component was cholesterol, constituting half the mixture, followed in order of decreasing concentration by 24α-ethylcholesterol (sitosterol), 24α-methylcholesterol (campesterol) and 24β-methylcholesterol (22-dihydrobrassicasterol). The relative amount of cholesterol in this plant is the highest found so far in a tracheophyte. The 4,4-dimethyl compounds (0.1% of wet wt) included lanosterol (5%), 24-dihydrolansterol (5%), β-amyrin (25%), germanicol (50%), an unidentified pentacyclic triterpenoid (8%) and two or more (7%) unidentified components. Both the 4,4-dimethyl- and the 4-desmethylsterols were in the configurational series with a 20α-H-atom. Dihydrolanosterol and lanosterol are the probable intermediates from cycloartenol to cholesterol and 24-alkylcholesterol, respectively. Such a sequence would differ from that operating in most angiosperms, where the alkylation is thought to precede the opening of the 9,19-cyclopropane ring.     

Effects of pulsed magnetic stimulation on isolated crayfish heart

ABSTRACT

Cardiac muscular contraction of the neurogenic heart that could be excited by pulsed magnetic stimulation (PMS) was investigated using preparation of the isolated crayfish heart. When a figure-eight magnetic coil was set over the isolated heart, cardiac contraction induced by a single PMS was not observed. Cardiac arrest occurred immediately after repetitive PMS and persisted for dozens of seconds depending on the number of stimuli. We concluded that PMS caused neuronal modulation in the neuronal network in the cardiac ganglion.     

NMR characterization of copper and lipid interactions of the C2B domain of synaptotagmin I—relevance to the non-classical secretion of the human acidic fibroblast growth factor (hFGF-1)

Human fibroblast growth factor (hFGF-1) is a ∼ 17 kDa heparin binding cytokine. It lacks the conventional hydrophobic N-terminal signal sequence and is secreted through non-classical secretion routes. Under stress, hFGF-1 is released as a multiprotein complex consisting of hFGF-1, S100A13 (a calcium binding protein), and p40 synaptotagmin (Syt1). Copper (Cu²⁺) is shown to be required for the formation of the multiprotein hFGF-1 release complex (Landriscina et al. ,2001; Di Serio et al., 2008). Syt1, containing the lipid binding C2B domain, is believed to play an important role in the eventual export of the hFGF-1 across the lipid bilayer. In this study, we characterize Cu²⁺ and lipid interactions of the C2B domain of Syt1 using multidimensional NMR spectroscopy. The results highlight how Cu²⁺ appears to stabilize the protein bound to pS vesicles. Cu²⁺ and lipid binding interface mapped using 2D ¹H-¹⁵N heteronuclear single quantum coherence experiments reveal that residues in β-strand I contributes to the unique Cu²⁺ binding site in the C2B domain. In the absence of metal ions, residues located in Loop II and β-strand IV contribute to binding to unilamelar pS vesicles. In the presence of Cu²⁺, additional residues located in Loops I and III appear to stabilize the protein-lipid interactions. The results of this study provide valuable information towards understanding the molecular mechanism of the Cu²⁺-induced non-classical secretion of hFGF-1.     

Studies on the possible biological effects of 50 Hz electric and/or magnetic fields: Evaluation of some glycolytic enzymes,glycolytic flux,energy and oxido-reductive potentials in human erythrocytes exposed in vitro to power frequency fields

An attempt has been made to understand whether 50 Hz electric and magnetic fields (EMFs) are involved in producing bioeffects by exposing human erythrocytes in vitro. The study evaluated some key glycolytic enzymes, glucose consumption, lactate production, energy charge, 2,3-diphosphoglycerate, and reduced glutathione levels. all of which are biochemical parameters significant to erythrocyte function. Cells exposed to individual or superimposed EMFs have not shown any significant difference compared with the controls. © 1993 Wiley-Liss. Inc.     

Neurochemical effects of a 20 kHz magnetic field on the central nervous system in prenatally exposed mice

C57/B1 mice were exposed during pregnancy (gestation days 0–19) to a 20 kHz magnetic field (MF). The asymmetric sawtooth-wave form magnetic field in the exposed racks had a flux density of 15 μT (peak to peak). After 19 days, the exposure was terminated, and the mice were housed individually under normal laboratory conditions. On postnatal day (PD) 1, PD21, and PD308, various neurochemical markers in the brains of the offspring were investigated and the brains weighed. No significant difference was found in the whole brain weight at PD1 or PD21 between exposed offspring and control animals. However, on PD308, a significant decrease in weight of the whole brain was detected in exposed animals. No significant differences were found in the weight of cortex, hippocampus, septum, or cerebellum on any of the sampling occasions, nor were any significant differences detected in protein-, DNA-level, nerve growth factor (NGF), acetylcholine esterase- (AChE), or 2′,3′-cyclic nucle-otide 3′-phosphodiesterase- (CNP; marker for oligodendrocytes) activities on PD21 in cerebellum. Cortex showed a more complex pattern of response to MF: MF treatment resulted in a decrease in DNA level and increases in the activities of CNP, AChE, and NGF protein. On PD308, the amount of DNA was significantly reduced in MF-treated cerebellum and CNP activity was still enhanced in MF-treated cortex compared to controls. Most of the effects of MF treatment during the embryonic period were similar to those induced by ionizing radiation but much weaker. However, the duration of the exposure required to elucidate the response of different markers to MF seems to be greater and effects appear later during development compared to responses to ionizing radiation. © 1995 Wiley-Liss, Inc.     

Effects of 50 Hz magnetic fields on mouse spermatogenesis monitored by flow cytometric analysis

Flow cytometry (FCM) was performed to monitor the cellular effects of extremely-low-frequency magnetic field on mouse spermatogenesis. Groups of five male hybrid F1 mice aged 8–10 weeks were exposed to 50 Hz magnetic field. The strength of the magnetic field was 1.7 mT. Exposure times of 2 and 4 h were chosen. FCM measurements were performed 7, 14, 21, 28, 35, and 42 days after treatment. For each experimental point, a sham-treated group was used as a control. The possible effects were studied by analyzing the DNA content distribution of the different cell types involved in spermatogenesis and using the elongated spermatids as the reference population. The relative frequencies of the various testicular cell types were calculated using specific software. In groups exposed for 2 h, no effects were observed. In groups exposed for 4 h, a statistically significant (P < 0.001) decrease in elongated spermatids was observed at 28 days after treatment. This change suggests a possible cytotoxic and/or cytostatic effect on differentiating spermatogonia. However, further studies are being carried out to investigate the effects of longer exposure times. © 1995 Wiley-Liss, Inc.     

Gadolinium-containing carbon nanomaterials for magnetic resonance imaging: Trends and challenges

Gadolinium-containing carbon nanomaterials are a new class of contrast agent for magnetic resonance imaging. They are characterized by a superior proton relaxivity to any current commercial gadolinium contrast agent and offer the possibility to design multifunctional contrasts. Intense efforts have been made to develop these nanomaterials because of their potential for better results than the available gadolinium contrast agents. The aim of the present work is to provide a review of the advances in research on gadolinium-containing carbon nanomaterials and their advantages over conventional gadolinium contrast agents. Due to their enhanced proton relaxivity, they can provide a reliable imaging contrast for cells, tissues or organs with much smaller doses than currently used in clinical practice, thus leading to reduced toxicity (as shown by cytotoxicity and biodistribution studies). Their active targeting capability allows for improved MRI of molecular or cellular targets, overcoming the limited labelling capability of available contrast agents (restricted to physiological irregularities during pathological conditions). Their potential of multifunctionality encompasses multimodal imaging and the combination of imaging and therapy.     

A novel electroconductive interface based on Fe3O4 magnetic nanoparticle and cysteamine functionalized AuNPs: Preparation and application as signal amplification element to minoring of antigen‐antibody immunocomplex and biosensing of prostate cancer

In this study, a novel electroconductive interface was prepared based on Fe₃O₄ magnetic nanoparticle and cysteamine functionalized gold nanoparticle. The engineered interface was used as signal amplification substrate in the electrochemical analysis of antibody‐antigen binding. For this purpose, biotinilated‐anti‐prostate‐specific antigen (PSA) antibody was bioconjugated with iron oxide magnetic nanoparticles (Fe₃O₄) and drop‐casted on the surface of glassy carbon electrode (GCE). Also, secondary antibody (HRP‐Ab2) encapsulated on gold nanoparticles caped by cysteamine was immobilized on the surface of GCE modified electrode. A transmission electron microscopy images shows that a sandwich immunoreaction was done and binding of Ab1 and Ab2 performed successfully. Various parameters of immunoassay, including the loading of magnetic nanoparticles, the amount of gold nanoparticle conjugate, and the immunoreaction time, were optimized. The detection limit of 0.001 μg. L^?1 of PSA was obtained under optimum experimental conditions. It is found that such magneto‐bioassay could be readily used for simultaneous parallel detection of multiple proteins by using multiple inorganic metal nanoparticle tracers and are expected to open new opportunities for early stage diagnosis of cancer in near future.