Adsorption of (Phe-h5)/(Phe-d5)-substituted peptides from neurotensin family on the nanostructured surfaces of Ag and Cu: SERS studies.

This work describes an application of Raman (RS) and surface-enhanced Raman scattering (SERS) to characterize the selective adsorption of two peptides belonging to the neurotensin family peptides, such as kinetensin (KN) and xenopsin-related peptide 2 (XP-2) that are known to stimulate the growth of human tumors. To perform a reliable analysis of SERS spectra, the L-Phe residue (at position 8 or 1 in the amino acid sequence of these peptides) was replaced with L-Phe-d5 (five protons of L-phenylalanine ring substituted by deuterium). Native and (Phe-d5)-isotopically labeled peptides were deposited on electrochemically nanostructured surfaces of Ag (AgORC) and Cu (CuORC) from an aqueous solution (H2O). To determine the share of amide bonds in the interaction with the metallic substrate, SERS spectra of peptides adsorbed on AgORC from heavy water (D2O) were measured. Also, to determine the effect of the C-end on the SERS spectrum, measurements were made for the KN analog in which the C-terminal L-leucine was removed ([desLeu9]KN). Based on the analyses of the spectral profiles, in the spectral range of 600-1650 cm-1, specific conclusions have been drawn regarding specific aromatic ring···metal interactions and changes in the interaction during substrate change.

Detection of circulating tumor cells in blood by shell-isolated nanoparticle - enhanced Raman spectroscopy (SHINERS) in microfluidic device.

Isolation and detection of circulating tumor cells (CTCs) from human blood plays an important role in non- invasive screening of cancer evolution and in predictive therapeutic treatment. Here, we present the novel tool utilizing: (i) the microfluidic device with (ii) incorporated photovoltaic (PV) based SERS-active platform, and (iii) shell-isolated nanoparticles (SHINs) for simultaneous separation and label-free analysis of circulating tumour cells CTCs in the blood specimens with high specificity and sensitivity. The proposed microfluidic chip enables the efficient size - based inertial separation of circulating cancer cells from the whole blood samples. The SERS-active platform incorporated into the microfluidic device permits the label-free detection and identification of isolated cells through the insight into their molecular and biochemical structure. Additionally, the silver nanoparticles coated with an ultrathin shell of silica (Ag@SiO2) was used to improve the detection accuracy and sensitivity of analysed tumor cells via taking advantages of shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). The empirical analysis of SHINERS spectra revealed that there are some differences among studied (HeLa), renal cell carcinoma (Caki-1), and blood cells. Unique SHINERS features and differences in bands intensities between healthy and cancer cells might be associated with the variations in the quantity and quality of molecules such as lipid, protein, and DNA or their structure during the metastasis cancer formation. To demonstrate the statistical efficiency of the developed method and improve the differentiation for circulating tumors cells detection the principal component analysis (PCA) has been performed for all SHINERS data. PCA method has been applied to recognize the most significant differences in SHINERS data among the three analyzed cells: Caki-1, HeLa, and blood cells. The proposed approach challenges the current multi-steps CTCs detection methods in the terms of simplicity, sensitivity, invasiveness, destructivity, time and cost of analysis, and also prevents the defragmentation/damage of tumor cells and thus leads to improving the accuracy of analysis. The results of this research work show the potential of developed SERS based tool for the separation of tumor cells from whole blood samples in a simple and minimally invasive manner, their detection and molecular characterization using one single technology.

Optically probing the fine structure of a single Mn atom in an InAs quantum dot.

We report on the optical spectroscopy of a single InAs/GaAs quantum dot doped with a single Mn atom in a longitudinal magnetic field of a few Tesla. Our findings show that the Mn impurity is a neutral acceptor state A0 whose effective spin J=1 is significantly perturbed by the quantum dot potential and its associated strain field. The spin interaction with photocarriers injected in the quantum dot is shown to be ferromagnetic for holes, with an effective coupling constant of a few hundreds of mueV, but vanishingly small for electrons.

Ravidomycin (AY-25,545), a new antitumor antibiotic.

A streptomycete was isolated from a Guatemala soil sample and found to inhibit Grampositive bacteria including mycobacteria. The antibiotic-producing microorganism was characterized, identified as a new species and named Streptomyces ravidus. The antibiotic principle was extracted with organic solvent from the mycelium, isolated in crystalline form and named ravidomycin. Ravidomycin is mainly active against Gram-positive bacteria including mycobacteria. It shows only weak activity against Gram-negative organisms and no activity against fungi. Ravidomycin exhibits potent antitumor activity against P388 lymphocytic leukemia, Colon 38 tumor and CD8F1 mammary tumor. Acute toxicity in mice is low.

Biosynthesis of kitasamycin (leucomycin) by leucine analog-resistant mutants of Streptomyces kitasatoensis.

The biosynthesis of kitasamycin in Streptomyces kitasatoensis B-896 was profoundly influenced by the addition of precursors to complex and defined media: l-valine and l-leucine directed biosynthesis towards the pairs A(4)/A(5) (R(2) = butyryl) and A(1)/A(3) (R(2) = isovaleryl), respectively, and total kitasamycin titers were doubled and quadrupled, respectively. S. kitasatoensis B-896 was very resistant (>20 mg/ml) to alpha-aminobutyric acid, an analog of l-valine, but very susceptible to l-leucine analogs 5', 5', 5'-trifluoroleucine and 4-azaleucine (5 to 10 mug/ml). The inhibition by 4-azaleucine could be reversed by l-leucine, but by none of the other amino acids of the pyruvate family or the amino acids of the aspartate pathway. 4-Azaleucine-resistant mutants were isolated which in the absence of any precursors overproduced l-leucine and a kitasamycin complex mainly consisting of the pair A(1)/A(3). These 4-azaleucine-resistant mutants are presumed to be regulatory mutants in which alpha-isopropylmalate synthase, the first enzyme of the l-leucine pathway, has become either derepressed or desensitized to leucine feedback inhibition. l-Leucine-regulatory mutants have economic value: in the absence of expensive precursors, they produce a kitasamycin complex in which the most potent pair A(1)/A(3) is dominant and the least active components are absent.

Antimycin A fermentation. I. Production and selection of strains.

Increase in antimycin A production was achieved through a parallel strain and medium improvement program: a 125-fold augmentation (75 to 9,500 mug/ml) was obtained. The selective system included antimycin A productivity, conidiation, sensitivity to ultraviolet radiation, growth rate and yield, and absence of pigment and actinomycin D production. Among the original strains tested one natural isolate possessed high productivity and several of the above characteristics, and was selected for mutagenesis. Spontaneous and induced variability was then exploited in isolating high-producing strains. The first mutagen used was ultraviolet radiation; it was replaced by ethylenimine when it became no longer efficient in increasing variability. As new, high producers were isolated, the medium was modified to best suit their requirements for still higher productivity. The critical environmental factors were absence of phosphate and organic salts, concentration of the nitrogen source and ratio organic/inorganic nitrogen, ratio ammonium sulfate/calcium carbonate, and addition of slowly utilizable carbon sources, such as lactose and oil; optimum temperature and initial pH were 25 degrees C and 7.0. Aeration/agitation requirements of improved strains were high. Fermentation was characterized by abrupt pH changes which impaired rapid accumulation of the antibiotic. Antimycin A was produced during both the trophophase and idiophase.

Rapamycin (AY-22,989), a new antifungal antibiotic. I. Taxonomy of the producing streptomycete and isolation of the active principle.

A streptomycete was isolated from an Easter Island soil sample and found to inhibit Candida albicans, Microsporum gypseum and Trichophyton granulosum. The antibiotic-producing microorganism was characterized and identified as Streptomyces hygroscopicus. The antifungal principle was extracted with organic solvent from the mycelium, isolated in crystalline form and named rapamycin. Rapamycin is mainly active against Candida albicans; minimum inhibitory concentration against ten strains ranged from 0.02 to 0.2 mug/ml. Its apparent activity against Microsporum gypseum and Trichophyton granulosum is lower because of its instability in culture media on prolonged incubation required by these fungi. No activity was observed against gram-positive and gram-negative bacteria. Acute toxicity in mice is low.