Vibrational spectroscopies for biochemical investigation of X-ray exposure effects on SH-SY5Y human neuroblastoma cells

Neuroblastoma is the most recurring cancer in childhood and adolescence. The SH-SY5Y neuroblastoma cell line is generally adopted for elaborating new therapeutical approaches and/or elaborating strategies for the prevention of central nervous system disturbances. In fact, it represents a valid model system for investigating in vitro the effects on the brain of X-ray exposure using vibrational spectroscopies that can detect early radiation-induced molecular alterations of potential clinical usefulness. In recent years, we dedicated significant efforts in the use of Fourier-transform and Raman microspectroscopy techniques for characterizing such radiation-induced effects on SH-SY5Y cells by examining the contributions from different cell components (DNA, proteins, lipids, and carbohydrates) to the vibrational spectra. In this review, we aim at revising and comparing the main results of our studies to provide a wide outlook of the latest outcomes and a framework for future radiobiology research using vibrational spectroscopies. A short description of our experimental approaches and data analysis procedures is also reported.

Wine yeast selection in the Iberian Peninsula: Saccharomyces and non-Saccharomyces as drivers of innovation in Spanish and Portuguese wine industries

Yeast selection for the wine industry in Spain started in 1950 for the understanding of the microbial ecology, and for the selection of optimal strains to improve the performance of alcoholic fermentation and the overall wine quality. This process has been strongly developed over the last 30 years, firstly on Saccharomyces cerevisiae, and, lately, with intense activity on non-Saccharomyces. Several thousand yeast strains have been isolated, identified and tested to select those with better performance and/or specific technological properties. The present review proposes a global survey of this massive ex-situ preservation of eukaryotic microorganisms, a reservoir of biotechnological solutions for the wine sector, overviewing relevant screenings that led to the selection of strains from 12 genera and 22 species of oenological significance. In the first part, the attention goes to the selection programmes related to relevant wine-producing areas (i.e. Douro, Extremadura, Galicia, La Mancha and Uclés, Ribera del Duero, Rioja, Sherry area, and Valencia). In the second part, the focus shifted on specific non-Saccharomyces genera/species selected from different Spanish and Portuguese regions, exploited to enhance particular attributes of the wines. A fil rouge of the dissertation is the design of tailored biotechnological solutions for wines typical of given geographic areas.

Discrimination of Different Breast Cell Lines on Glass Substrate by Means of Fourier Transform Infrared Spectroscopy

Fourier transform infrared (FTIR) micro-spectroscopy has been attracting the interest of many cytologists and histopathologists for several years. This is related to the possibility of FTIR translation in the clinical diagnostic field. In fact, FTIR spectra are able to detect changes in biochemical cellular components occurring when the cells pass to a pathological state. Recently, this interest has increased because it has been shown that FTIR spectra carried out just in the high wavenumber spectral range (2500-4000 cm^-1), where information mainly relating to lipids and proteins can be obtained, are able to discriminate cell lines related to different tissues. This possibility allows to perform IR absorption measurements of cellular samples deposited onto microscopy glass slides (widely used in the medical environment) which are transparent to IR radiation only for wavenumber values larger than 2000 cm^-1. For these reasons, we show that FTIR spectra in the 2800-3000 cm^-1 spectral range can discriminate three different cell lines from breast tissue: a non-malignant cell line (MCF10A), a non-metastatic adenocarcinoma cell line (MCF7) and a metastatic adenocarcinoma cell line (MDA). All the cells were grown onto glass slides. The spectra were discriminated by means of a principal component analysis, according to the PC1 component, whose values have the opposite sign in the pairwise score plots. This result supports the wide studies that are being carried out to promote the translation of the FTIR technique in medical practice, as a complementary diagnostic tool.

Recognition of healthy and cancerous breast cells: Sensing the differences by dielectric spectroscopy

PURPOSE

The response of human cells to applied electrical signals depends on the cellular health status, because it is influenced by the composition and structure of the main cellular components. Therefore, electrical impedance-based techniques can be considered as sensitive tools to investigate healthy or disease state at cellular level. The goal of this study is to show that different types of in vitro cellular lines, related to different health status, can be differentiated using impedance spectra analysis.

METHODS

Three different types of human breast cell line, corresponding to healthy, cancerous, and metastatic adenocarcinoma cells, were measured by means of electrical impedance spectroscopy. By modeling the investigated cells with proper resistive and capacitive circuital elements, the magnitude of the cell electrical components and spectra of real and imaginary part of dielectric permittivity were obtained. The latter were subsequently examined with a commonly adopted mathematical model, in order to estimate the values of specific dielectric parameters for the three different cellular lines.

RESULTS

The relative variation of cellular capacitance with respect to that of the culture medium, estimated at 100 Hz, has a larger value for the two types of cancerous cells with respect to the noncancerous type. Furthermore, the ratio between the real and imaginary part of the dielectric permittivity function has larger values for metastatic cells with respect to the normal and nonmetastatic ones. Therefore, the mentioned relative capacitance allows to discriminate between normal and cancerous cells, whereas the results obtained for the dielectric function can discriminate between metastatic and nonmetastatic cells.

CONCLUSIONS

This study can be considered as an exploratory investigation of evaluating in vitro the health status of humans cells using selected electrical impedance parameters as potential markers. The obtained results highlight that a standard cultureware system, provided with interdigitated electrodes and appropriate impedance parameters, that is, cellular capacitance and the ratio between the imaginary and real part of cellular dielectric function, can be used to discriminate between healthy and cancerous breast cell lines, as well as different malignancy degrees.

Raman spectroscopy for the evaluation of the radiobiological sensitivity of normal human breast cells at different time points after irradiation by a clinical proton beam

Radiobiological effects occurring in normal human breast cells exposed to a low dose of a clinical proton beam are detectable by means of Raman spectra and the ratiometric analysis of Raman peak intensities.

Correction: Exposure to 1.8 GHz electromagnetic fields affects morphology, DNA-related Raman spectra and mitochondrial functions in human lympho-monocytes

[This corrects the article DOI: 10.1371/journal.pone.0192894.].

Evaluation of PTR-ToF-MS as a tool to track the behavior of hop-derived compounds during the fermentation of beer

Hop-derived volatile organic compounds (VOCs) play an important role in the flavor and aroma of beer, despite making up a small percentage of the overall profile. To understand the changes happening during fermentation, proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS) was applied for the first time in brewing science to directly measure the changes in hop-derived VOCs during the fermentation of four different worts containing one of two aroma hops in combination with one of two yeast biotypes. PTR-ToF-MS successfully detected and tracked mass-to-charge ratios (m/z) arising from interactions between the different yeast strains and the hop cultivars. Differences were observed in the dynamic VOC profiles between different beer treatments for m/z such as m/z 145.121 (ethyl hexanoate) and m/z 173.153 (isoamyl isovalerate or ethyl octanoate). The ability to monitor changes in VOCs during fermentation provides valuable information on the priority of production and transformation reactions by yeast.

Exposure to 1.8 GHz electromagnetic fields affects morphology, DNA-related Raman spectra and mitochondrial functions in human lympho-monocytes

Blood is a fluid connective tissue of human body, where it plays vital functions for the nutrition, defense and well-being of the organism. When circulating in peripheral districts, it is exposed to some physical stresses coming from outside the human body, as electromagnetic fields (EMFs) which can cross the skin. Such fields may interact with biomolecules possibly inducing non thermal-mediated biological effects at the cellular level. In this study, the occurrence of biochemical/biological modifications in human peripheral blood lympho-monocytes exposed in a reverberation chamber for times ranging from 1 to 20 h to EMFs at 1.8 GHz frequency and 200 V/m electric field strength was investigated. Morphological analysis of adherent cells unveiled, in some of these, appearance of an enlarged and deformed shape after EMFs exposure. Raman spectra of the nuclear compartment of cells exposed to EMFs revealed the onset of biochemical modifications, mainly consisting in the reduction of the DNA backbone-linked vibrational modes. Respirometric measurements of mitochondrial activity in intact lympho-monocytes resulted in increase of the resting oxygen consumption rate after 20 h of exposure, which was coupled to a significant increase of the FoF1-ATP synthase-related oxygen consumption. Notably, at lower time-intervals of EMFs exposure (i.e. 5 and 12 h) a large increase of the proton leak-related respiration was observed which, however, recovered at control levels after 20 h exposure. Confocal microscopy analysis of the mitochondrial membrane potential supported the respiratory activities whereas no significant variations in the mitochondrial mass/morphology was observed in EMFs-exposed lympho-monocytes. Finally, altered redox homeostasis was shown in EMFs-exposed lympho-monocytes, which progressed differently in nucleated cellular subsets. This results suggest the occurrence of adaptive mechanisms put in action, likely via redox signaling, to compensate for early impairments of the oxidative phosphorylation system caused by exposure to EMFs. Overall the data presented warn for health safety of people involved in long-term exposure to electromagnetic fields, although further studies are required to pinpoint the leukocyte cellular subset(s) selectively targeted by the EMFs action and the mechanisms by which it is achieved.

Human airway epithelial cells investigated by atomic force microscopy: A hint to cystic fibrosis epithelial pathology

The pathophysiology of cystic fibrosis (CF) airway disease stems from mutations in the CF Transmembrane Conductance Regulator (CFTR) gene, leading to a chronic respiratory disease. Actin cytoskeleton is disorganized in CF airway epithelial cells, likely contributing to the CF-associated basic defects, i.e. defective chloride secretion and sodium/fluid hypersorption. In this work, we aimed to find whether this alteration could be pointed out by means of Atomic Force Microscopy (AFM) investigation, as roughness and Young's elastic module. Moreover, we also sought to determine whether disorganization of actin cytoskeleton is linked to hypersoption of apical fluid. Not only CFBE41o- (CFBE) cells, immortalized airway epithelial cells homozygous for the F508del CFTR allele, showed a different morphology in comparison with 16HBE14o- (16HBE) epithelial cells, wild-type for CFTR, but also they displayed a lack of stress fibers, suggestive of a disorganized actin cytoskeleton. AFM measurements showed that CFBE cells presented a higher membrane roughness and decreased rigidity as compared with 16HBE cells. CFBE overexpressing wtCFTR became more elongated than the parental CFBE cell line and presented actin stress fibers. CFBE cells absorbed more fluid from the apical compartment. Study of fluid absorption with the F-actin-depolymerizing agent Latrunculin B demonstrated that actin cytoskeletal disorganization increased fluid absorption, an effect observed at higher magnitude in 16HBE than in CFBE cells. For the first time, we demonstrate that actin cytoskeleton disorganization is reflected by AFM parameters in CF airway epithelial cells. Our data also strongly suggest that the lack of stress fibers is involved in at least one of the early step in CF pathophysiology at the levels of the airways, i.e. fluid hypersorption.

Characterization of obstructive sleep apnea-hypopnea syndrome (OSA) population by means of cluster analysis

Obstructive sleep apnea-hypopnea syndrome (OSA) is being identified increasingly as an important health issue. It is typified by repeated episodes of upper airway collapse during sleep leading to occasional hypoxaemia, sleep fragmentation and poor sleep quality. OSA is also being considered as an independent risk factor for hypertension, diabetes and cardiovascular diseases, leading to increased multi-morbidity and mortality. Cluster analysis, a powerful statistical set of techniques, may help in investigating and classifying homogeneous groups of patients with similar OSA characteristics. This study aims to investigate the (possible) different groups of patients in an OSA population, and to analyse the relationships among the main clinical variables in each group to better understand the impact of OSA on patients. Starting from a well-characterized OSA population of 198 subjects afferent to our sleep centre, we identified three different communities of OSA patients. The first has a very severe disease [apnea-hypopnea index (AHI) = 65.91 ± 22.47] and sleep disorder has a strong impact on daily life: a low level of diurnal partial pressure of oxygen (PaO₂ ) (77.39 ± 11.64 mmHg) and a high prevalence of hypertension (64%); the second, with less severe disease (AHI = 28.88 ± 17.13), in which sleep disorders seem to be less important for diurnal PaO₂ and have a minimum impact on comorbidity; and the last with very severe OSA (AHI = 57.26 ± 15.09) but with a low risk of nocturnal hypoxaemia (T90 = 11.58 ± 8.54) and less sleepy (Epworth Sleepiness Scale 10.00 ± 4.77).

Ultrafast transient absorption of eumelanin suspensions: the role of inverse Raman scattering

An ultrafast investigation is carried out on synthetic eumelanin suspended either in water or in DMSO-methanol. Upon photoexcitation by visible femtosecond pulses, the transient absorption (TA) dynamics of the suspensions are probed in a broad visible spectral range, showing clear nonlinearities. The latter arise from pump-probe interactions that induce the inverse Raman scattering (IRS) effect. We show how eumelanin TA dynamics are modified in proximity of the solvent Stokes and anti-Stokes scattering peaks, demonstrating that IRS affects the sign of TA but not the relaxation times. We compare the results obtained in both suspensions, unveiling the role of the surrounding environment. Eventually, the intrinsic response of synthetic eumelanin to ultrafast photoexcitation is evaluated.

Visible micro-Raman spectroscopy of single human mammary epithelial cells exposed to x-ray radiation

A micro-Raman spectroscopy investigation has been performed in vitro on single human mammary epithelial cells after irradiation by graded x-ray doses. The analysis by principal component analysis (PCA) and interval-PCA (i-PCA) methods has allowed us to point out the small differences in the Raman spectra induced by irradiation. This experimental approach has enabled us to delineate radiation-induced changes in protein, nucleic acid, lipid, and carbohydrate content. In particular, the dose dependence of PCA and i-PCA components has been analyzed. Our results have confirmed that micro-Raman spectroscopy coupled to properly chosen data analysis methods is a very sensitive technique to detect early molecular changes at the single-cell level following exposure to ionizing radiation. This would help in developing innovative approaches to monitor radiation cancer radiotherapy outcome so as to reduce the overall radiation dose and minimize damage to the surrounding healthy cells, both aspects being of great importance in the field of radiation therapy.

Discrimination of different degrees of oral squamous cell carcinoma by means of Raman microspectroscopy and atomic force microscopy

Two cellular types characterized by different degree of oral squamous cell carcinoma can be discriminated by Raman microspectroscopy and Atomic Force Microscopy, according to the content of nucleic acids and proteins as well as the membrane stiffness.

Raman spectroscopy of human neuronal and epidermal cells exposed to an insecticide mixture of chlorpyrifos and deltamethrin

Many pesticides are increasingly used in combinations for crop protection. Their chemical stability ensures the presence of such mixtures, both in the workspaces of the operators involved in agricultural activities and in foodstuffs, thus making probable human exposure to such chemicals in the environment. This investigation, performed by means of Raman microspectroscopy and principal component analysis, concerns the effects of in vitro cellular exposure to a commercial insecticide based on a chlorpyrifos and deltamethrin mixture. The investigated cells belong to the SHSY-5Y and human keratinocyte (HUKE) cell lines, which can be considered representative of neuronal and epidermal cells, respectively. After 24 h exposure at a concentration one-tenth of that usually used by operators, about 50% of the investigated cells were dead and the relative content of the biochemical components of both types of cells that were still alive had been affected by the exposure. A statistically significant decrease in the protein and nucleic acid content occurred in the SHSY-5Y cells, and a lowering of the lipid and carbohydrate content was observed in the HUKE cells. This study shows the utility of Raman microspectroscopy and principal component analysis for the investigation of the effects on human cells of environmental exposure to any chemicals.

Localized surface plasmon resonances in gold nano-patches on a gallium nitride substrate

In this paper we describe the design, fabrication and characterization of gold nano-patches, deposited on gallium nitride substrate, acting as optical nanoantennas able to efficiently localize the electric field at the metal-dielectric interface. We analyse the performance of the proposed device, evaluating the transmission and the electric field localization by means of a three-dimensional finite difference time domain (FDTD) method. We detail the fabrication protocol and show the morphological characterization. We also investigate the near-field optical transmission by means of scanning near-field optical microscope measurements, which reveal the excitation of a localized surface plasmon resonance at a wavelength of 633 nm, as expected by the FDTD calculations. Such results highlight how the final device can pave the way for the realization of a single optical platform where the active material and the metal nanostructures are integrated together on the same chip.

Scale-independent roughness value of cell membranes studied by means of AFM technique

The roughness of cell membrane is a very interesting indicator of cell's health state. Atomic Force Microscopy allows us to investigate the roughness of cell membrane in great detail, but the obtained roughness value is scale-dependent, i.e. it strongly depends on measurement parameters, as scanning area and step size. The scale-dependence of the roughness value can be reduced by means of data filtration techniques, that are not standardized at nanometric scale, especially as far as biological data are concerned. In this work, a new method, based on the changes of values of some roughness parameter (root mean square roughness and skewness) as a function of filtration frequencies, has been implemented to optimize data filtering procedure in the calculation of cell membrane roughness. In this way, a root mean square roughness value independent of cell shape, membrane micro-irregularities and measurement parameters can be obtained. Moreover, different filtration frequencies selected with this method allow us to discriminate different surface regimes (nominal form, waviness and roughness) belonging to the raw cell profile, each one related to different features of the cell surface.

Micro-Raman spectroscopy and univariate analysis for monitoring disease follow-up

Micro-Raman spectroscopy is a very promising tool for medical applications, thanks to its sensitivity to subtle changes in the chemical and structural characteristics of biological specimens. To fully exploit these promises, building a method of data analysis properly suited for the case under study is crucial. Here, a linear or univariate approach using a R2 determination coefficient is proposed for discriminating Raman spectra even with small differences. The validity of the proposed approach has been tested using Raman spectra of high purity glucose solutions collected in the 600 to 1,600 cm(-1) region and also from solutions with two known solutes at different concentrations. After this validation step, the proposed analysis has been applied to Raman spectra from oral human tissues affected by Pemphigus Vulgaris (PV), a rare life-threatening autoimmune disease, for monitoring disease follow-up. Raman spectra have been obtained in the wavenumber regions from 1,050 to 1,700 cm(-1) and 2,700 to 3,200 cm(-1) from tissues of patients at different stages of pathology (active PV, under therapy and PV in remission stage) as confirmed by histopathological and immunofluorescence analysis. Differences in the spectra depending on tissue illness stage have been detected at 1,150-1,250 cm(-1) (amide III) and 1,420-1,450 cm(-1) (CH3 deformation) regions and around 1,650 cm(-1) (amide I) and 2,930 cm(-1) (CH3 symmetric stretch). The analysis of tissue Raman spectra by the proposed univariate method has allowed us to effectively differentiate tissues at different stages of pathology.

Laser Ablation of Highly Oriented Cdse Thin Films and Cdte/Cdse Multilayers on Silicon Substrate

Laser ablation technique has been successfully used for the deposition of CdSe and CdTe/CdSe multilayers on Si(100) and Si(l11) substrates. X-ray analysis showed that CdSe/Si films were highly oriented. Their orientation changed from (100) to (002) by varying the substrate temperature from 473 to 673K. High orientation was also obtained on multilayered polycrystalline structures of CdSe and CdTe on Si(lll). Photoluminescence experiments have also been carried out on the deposited films.

Technological properties of Oenococcus oeni strains isolated from typical southern Italian wines

AIMS

To isolate indigenous Oenococcus oeni strains suitable as starters for malolactic fermentation (MLF), using a reliable polyphasic approach.

METHODS AND RESULTS

Oenococcus oeni strains were isolated from Nero di Troia wines undergoing spontaneous MLF. Samples were taken at the end of alcoholic fermentation and during MLF. Wine samples were diluted in a sterile physiological solution and plated on MRS and on modified FT80. Identification of O. oeni strains was performed by a polymerase chain reaction (PCR) experiment using strain-specific primers. Strains were further grouped using a multiplex RAPD-PCR analysis. Then, six strains were inoculated in two winelike media with two different ethanol concentrations (11 and 13% vol / vol) with a view to evaluate their capacity to grow and to perform MLF. In addition, a quantitative PCR (qRT-PCR) approach was adapted to monitor the physiological state of the strains selected.

CONCLUSION

A positive correlation between the malolactic activity performance and the ability to develop and tolerate stress conditions was observed for two selected O. oeni strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results reported are useful for the selection of indigenous MLF starter cultures with desired oenological traits from typical regional wines. It should be the base for the improvement in organoleptic quality of typical red wine.

An Investigation on Micro-Raman Spectra and Wavelet Data Analysis for Pemphigus Vulgaris Follow-up Monitoring

A wavelet multi-component decomposition algorithm has been used for data analysis of micro-Raman spectra of blood serum samples from patients affected by pemphigus vulgaris at different stages. Pemphigus is a chronic, autoimmune, blistering disease of the skin and mucous membranes with a potentially fatal outcome. Spectra were measured by means of a Raman confocal microspectrometer apparatus using the 632.8 nm line of a He-Ne laser source. A discrete wavelet transform decomposition method has been applied to the recorded Raman spectra in order to overcome problems related to low-level signals and the presence of noise and background components due to light scattering and fluorescence. This numerical data treatment can automatically extract quantitative information from the Raman spectra and makes more reliable the data comparison. Even if an exhaustive investigation has not been done in this work, the feasibility of the follow-up monitoring of pemphigus vulgaris pathology has been clearly proved with useful implications for the clinical applications.

Topological organization of NADPH-oxidase in haematopoietic stem cell membrane: preliminary study by fluorescence near-field optical microscopy

The aim of this study was to characterize the local distribution and organization of the plasma membrane NADPH-oxidase (NOX) in human haematopoietic stem cell (HSC) by means of the fluorescence scanning near-field optical microscopy approach. The presence of NOX in haematopoietic stem cells is thought to have a functional role as O(2) sensor and/or as low-level reactive oxygen species (ROS) producer to be used as redox messenger for controlling cell growth and differentiation. Given the harmful potential of ROS, a fine-tuning of NOX activity is needed. The high resolution imaging of haematopoietic stem cell membrane obtained in this study combined with the immunodetection of NOX indicates for this the occurrence of a cluster-organized structure. These membrane 'rafts'-like micro-compartments may constitute localized protein aggregates whereby the assembly/activation of the NOX components are functionally integrated with upstream factors constituting signal-transduction platforms.

Radiofrequency radiation (900 MHz) induces Egr-1 gene expression and affects cell-cycle control in human neuroblastoma cells

Many environmental signals, including ionizing radiation and UV rays, induce activation of Egr-1 gene, thus affecting cell growth and apoptosis. The paucity and the controversial knowledge about the effect of electromagnetic fields (EMF) exposure of nerve cells prompted us to investigate the bioeffects of radiofrequency (RF) radiation on SH-SY5Y neuroblastoma cells. The effect of a modulated RF field of 900 MHz, generated by a wire patch cell (WPC) antenna exposure system on Egr-1 gene expression, was studied as a function of time. Short-term exposures induced a transient increase in Egr-1 mRNA level paralleled with activation of the MAPK subtypes ERK1/2 and SAPK/JNK. The effects of RF radiations on cell growth rate and apoptosis were also studied. Exposure to RF radiation had an anti-proliferative activity in SH-SY5Y cells with a significant effect observed at 24 h. RF radiation impaired cell cycle progression, reaching a significant G2-M arrest. In addition, the appearance of the sub-G1 peak, a hallmark of apoptosis, was highlighted after a 24-h exposure, together with a significant decrease in mRNA levels of Bcl-2 and survivin genes, both interfering with signaling between G2-M arrest and apoptosis. Our results provide evidence that exposure to a 900 MHz-modulated RF radiation affect both Egr-1 gene expression and cell regulatory functions, involving apoptosis inhibitors like Bcl-2 and survivin, thus providing important insights into a potentially broad mechanism for controlling in vitro cell viability.

The melanogenic system of the liver pigmented macrophages of Rana esculenta L.--tyrosinase activity

The enzyme system responsible for Amphibian Kupffer Cell (KC) melanogenesis has not been entirely elucidated. This research demonstrates that the KC melanosomes of Rana esculenta L. possess a tyrosine-hydroxylase (TH) activity, showing that a tyrosinase is the enzyme involved in the melanogenesis. The TH reaction depends on catalytic Dopa as a cofactor and is not affected by catalase or H2O2, showing that it is catalysed by the tyrosinase and not by the peroxidase present in the melanosomes. The TH reaction is activated by Cu2+ ions but not by other tyrosinase activators such as limited proteolysis, protein ageing, and Sodium Dodecyl Sulphate (SDS). SDS inhibited the KC TH activity even below the critical micelle concentration. All these results suggest that the KC-tyrosinase differs in structure from other known tyrosinases. Using anti-KC-tyrosinase antobodies, we observed that the sites of the tyrosinase location within the cell are the same as those described in the melanocytes. In the immunoblots, the anti-KC-tyrosinase antibodies also recognised two protein bands, at the higher molecular weight ranges, in the protein electrophoretic pattern. Moreover, the tyrosinase activity was limited to the highest molecular weight band of about 260 kDa, suggesting that the enzyme activity could depend on a molecular aggregate. The melanin produced in the liver was found to be a 5,6-dihydroxyindole-rich eumelanin similar to the Sepia melanin.

Cloning, molecular characterization and expression analysis of two small heat shock genes isolated from wine Lactobacillus plantarum

AIM

Understanding the molecular response to stress tolerance of wine Lactobacillus plantarum.

METHODS AND RESULTS

Two genes codifying for heat shock proteins were cloned from wine L. plantarum. The coding regions of the two heat shock genes are 420 and 444 nucleotides long, and started with an ATG codon suggesting that they were translated. The protein sequences deduced from the isolated genes have a molecular mass of 18.483 and 19.282 kDa, respectively, and were therefore named hsp18.5 and hsp19.3. The expression of small heat shock genes was analysed by RT-PCR analysis. Moreover, the 5' and 3' noncoding regions were cloned and sequenced.

CONCLUSIONS

The expression of the heat shock genes was strongly induced by heat, cold and ethanol stress. Analysis of the 5' and 3' flanking regions of hsp18.5 and hsp19.3 genes, revealed the presence of an inverted repeat sequence (TTAGCACTC-N(9)-GAGTGCTAA) homologue to the CIRCE elements found to the upstream regulatory region of heat shock operons, and an inverted sequence that could form a stem and loop structure that it is likely to function as a transcriptional terminator. Based on their structures, the genes were classified as belonging to Class I of heat shock genes according to the B. subtilis nomenclature of heat response genes.

SIGNIFICANCE AND IMPACT OF THE STUDY

Small heat shock genes isolated from wine L. plantarum might have a role in preventing damage by cold stress.

Noise dependence of correlation and structure functions on mean count rate and sampling time

Experimental results for the noise of photon-correlation and photon-structure functions are presented. The noise dependences on the mean count rate and on the sampling time are investigated by means of a specifically built linear fluctuation analyzer, and the results are compared with theoretical predictions. The predicted mean count rate dependence and sampling time dependence of the noise are confirmed by the experimental analysis. Some discrepancies between analytical expressions and experimental results are observed in the crossover predictions. The results show that the structure function has better noise performance for relatively high mean count rates and for long sampling times, which strongly suggests a wider use of this statistical estimator in measurements requiring good accuracy, as in the case of uniform sampling.