Occurrence and Characteristics of Toxigenic Staphylococcus aureus in Retail Foods in Iran.

Staphylococcus aureus causes various toxigenic and invasive diseases in humans worldwide. This study examined the prevalence, virulence genes, and antibiotic resistance of S. aureus isolates collected from 894 retail food samples in Ardabil, Iran. Staphylococcal cassette chromosome mec (SCCmec), spa, and multilocus sequence typing methods were employed to further investigate the molecular characteristics of methicillin-resistant S. aureus (MRSA) isolates. The results revealed that 11.18% (n = 100) of food samples exhibited contamination with S. aureus (10.50% methicillin-sensitive S. aureus [MSSA] and 0.67% MRSA). Notably, raw minced meat (29.41%), Faloodeh (25%), and Olivier salad (21.42%) emerged as the most frequently contaminated food items. Among the 100 isolates of S. aureus, 94% were characterized as MSSA, with the remaining 6% identified as MRSA. The highest resistance was observed for penicillin (12%). MRSA isolates exhibited significantly higher resistance rates. Seventy-nine percent of the isolates were positive for sea, 14% for seb, 8% for a sec, and 0% for sed enterotoxin-encoding genes. Sixteen percent of isolates harbored two or more staphylococcal enterotoxin genes, simultaneously. Moreover, 97%, 94%, 24%, and 22% of isolates were positive for hla, hld, tst, and pvl virulence-encoding genes, respectively. No isolate was positive for the exfoliative toxins encoding eta and etb genes. MRSA isolates belonged to CC8 (n = 4) and CC22 (n = 2). Isolates in CC8 belonged to lineage ST239-MRSA-III and spa type t030; the isolates in CC22 belonged to ST22-MRSA-IV and spa types t310 and t223. In conclusion, a relatively high proportion of our retail food samples were contaminated with S. aureus. The high incidence of isolates with toxigenic genes raises serious health concerns. Furthermore, the presence of MRSA lineages linked to humans suggests that retail foods may be contaminated with human origin.

Prevalence and mechanisms of ciprofloxacin resistance in Escherichia coli isolated from hospitalized patients, healthy carriers, and wastewaters in Iran.

BACKGROUND: This study was aimed to evaluate the prevalence and molecular characteristics of ciprofloxacin resistance among 346 Escherichia coli isolates collected from clinical specimens (n = 82), healthy children (n = 176), municipal wastewater (n = 34), hospital wastewater (n = 33), poultry slaughterhouse wastewater (n = 12) and livestock (n = 9) slaughterhouse wastewater in Iran. METHODS: Ciprofloxacin minimum inhibitory concentration (MIC) was determined by agar dilution assay. Phylogroups and plasmid-mediated quinolone resistance (PMQR) genes were identified using PCR. Mutations in gyrA, gyrB, parC, and parE genes and amino acid alterations were screened through sequencing assay. The effect of efflux pump inhibitor (PAßN) on ciprofloxacin MICs in ciprofloxacin-resistant isolates was investigated using the microdilution method. RESULTS: In total, 28.03% of E. coli isolates were phenotypically resistant to ciprofloxacin. Based on sources of isolation, 64.63%, 51.51%, 33.33%, 14.70%, 10.22% and 8.33% of isolates from clinical specimens, hospital wastewater, livestock wastewater, municipal wastewater, healthy children and poultry wastewater were ciprofloxacin-resistant, respectively. Eighty-one point eighty-one percent (Ser-83 → Leu + Asp-87 → Asn; 78.78% and Ser-83 → Leu only; 3.03% (of ciprofloxacin-resistant E. coli isolates showed missense mutation in GyrA subunit of DNA gyrase, while no amino-acid substitution was noted in the GyrB subunit. DNA sequence analyses of the ParC and ParE subunits of topoisomerase IV exhibited amino-acid changes in 30.30% (Ser-80 → Ile + Glu-84 → Val; 18.18%, Ser-80 → Ile only; 9.10% and Glu-84 → Val only; 3.03%0 (and 15.38% (Ser-458 → Ala) of ciprofloxacin-resistant E. coli isolates, respectively. The PMQR genes, aac(6')-Ib-cr, qnrS, qnrB, oqxA, oqxB, and qepA were detected in 43.29%, 74.22%, 9.27%, 14.43%, 30.92% and 1.03% of ciprofloxacin-resistant isolates, respectively. No isolate was found to be positive for qnrA and qnrD genes. In isolates harboring the OqxA/B efflux pump, the MIC of ciprofloxacin was reduced twofold in the presence of PAßN, as an efflux pump inhibitor. The phylogroups B2 (48.45%) and A (20.65%) were the most predominant groups identified in ciprofloxacin-resistant isolates. CONCLUSIONS: This study proved the high incidence of ciprofloxacin-resistant E. coli isolates in both clinical and non-clinical settings in Iran. Chromosomal gene mutations and PMQR genes were identified in ciprofloxacin resistance among E. coli population.

Sunset yellow degradation product, as an efficient water-soluble inducer, accelerates 1N4R Tau amyloid oligomerization: In vitro preliminary evidence against the food colorant safety in terms of "Triggered Amyloid Aggregation".

Today, Alzheimer's disease (AD) as the most prevalent type of dementia turns into one of the most severe health problems. Neurofibrillary tangle (NFT), mostly comprised of fibrils formed by Tau, is a hallmark of a class of neurodegenerative diseases. Tau protein promotes assembly and makes stable microtubules that play a role in the appropriate function of neurons. Polyanionic cofactors such as heparin, and azo dyes, can induce aggregation of tau protein in vitro. Sunset Yellow is a food colorant used widely in food industries. In the current work, we introduced degradation product (DP) of Sunset Yellow as an effective inducer of Tau aggregation. Two Tau aggregation inducers were produced, and then the aggregation kinetics and the structure of 1N4R Tau amyloid fibrils were characterized using ThT fluorescence spectroscopy, X-Ray Diffraction (XRD), circular dichroism (CD) and atomic force microscopy (AFM). Also, the toxic effects of the induced aggregates on RBCs and SH-SY5Y cells were demonstrated by hemolysis and LDH assays, respectively. Both inducers efficiently accelerated the formation of the amyloid fibril. Along with the confirmation of the ß-sheets structure in Tau aggregates by Far-UV CD spectra, X-ray diffractions revealed the typical cross-ß diffraction pattern. The oligomer formation in the presence of DPs was also confirmed by AFM. The possible in vivo effect of artificial azo dyes on Tau aggregation should be considered seriously as a newly opened dimension in food safety and human health.

Allicin prevents the formation of Proteus-induced urinary crystals and the blockage of catheter in a bladder model in vitro.

Stone formation and catheter blockage are major complications of Proteus UTIs. In this study, we investigated the ability of allicin to inhibit P. mirabilis-induced struvite crystallization and catheter blockage using a synthetic bladder model. Struvite crystallization inhibition study was carried out using P. mirabilis lysate as urease enzyme source in synthetic urine (SU). Struvite productions were monitored by phase contrast light microscopy and measurements of pH, Mg2+ and Ca2+ precipitation and turbidity. A catheter blockage study was performed in a synthetic bladder model mimicking natural UTI in the presence of allicin at sub-MIC concentrations (MIC = 64 µg/ml). The results of crystallization study showed that allicin inhibited pH rise and consequently turbidity and precipitation of ions in a dose-dependent manner. The results of catheter blockage study showed that allicin at sub-MIC concentrations (2, 4, 8 µg/ml) significantly increased the time for catheter blockage to occur to 61, 74 and 92 h respectively compared to allicin-free control (48 h). In a similar way, the results showed that allicin delayed the increase of SU pH level in bladder model in a dose-dependent manner compared to allicin-free control. The results also showed that following the increase of allicin concentration, Mg2+ and Ca2+ deposition in catheters were much lower compared to allicin-free control, further confirmed by direct observation of the catheters' eyehole and cross sections. We conclude that allicin prevents the formation of Proteus-induced urinary crystals and the blockage of catheters by delaying pH increase and lowering Mg2+ and Ca2+ deposition in a dose-dependent manner.

The effect of probiotic yoghurt consumption on oxidative stress and inflammatory factors in young females after exhaustive exercise.

OBJECTIVE: To evaluate the effect of probiotic yoghurt consumption on oxidative stress and inflammatory factors in young females after exhaustive exercise. METHODS: TThis study included 27 healthy participants with an age range of 18-25. For two weeks, 450 grams of probiotic yoghurt and 450 grams of ordinary yoghurt were given to the supplement and control groups, respectively. Fasting blood samples were taken at baseline and at the end of study. At the end of the intervention, the participants were given one exhaustive exercise and then fasting blood samples were taken to test for blood antioxidant enzymes, inflammatory markers, and oxidative markers. Data were analyzed using descriptive statistics as well as paired and independent samples t-test. RESULTS: In supplement group, the glutathione peroxidise (GPX) blood levels and serum levels of total antioxidant capacity (TAC) significantly increased at the end of two weeks of intervention (p<0.05). After intense physical activity, the blood levels of superoxide dismutase (SOD), GPX and serum levels of TAC significantly increased, whereas the serum level of tumour necrosis factor alpha (TNF-?), matrix metalloproteinase 2 (MMP2), matrix metalloproteinase 9 (MMP9), and malondialdehyde (MDA) significantly decreased in the supplement group compared to the control group (p<0.05). Besides, there were no significant changes in other biochemical factors. CONCLUSIONS: Regular probiotic yoghurt consumption significantly modulated MMP2, MMP9 and some inflammatory factors, and thus guarded against exhaustive exercise-inducing oxidative injury in young healthy females.

Anti-inflammatory effects of conjugated linoleic acid on young athletic males.

OBJECTIVE: To explore the efficacy of conjugated linoleic acid supplementation on some inflammatory factors in young healthy males during exhaustive exercise. METHODS: The randomised double-blind controlled study was conducted at Ardabil University of Medical Sciences, Iran, from December 2012 to March2013, and comprised healthy male athletes 18-24 years of age. The subjects were randomly distributed into control and intervention groups. About 5.6 g/day conjugated linoleic acid supplement and oral paraffin (placebo) were given to intervention and control groups respectively daily for two weeks. Fasting blood samples were taken at baseline and at the end of the two weeks of intervention. The subjects underwent exhaustive exercise and then fasting blood samples were taken. Serum levels of tumour necrosis factor alpha, interleukin-6, high-sensitivity C-reactive protein, matrix metalloproteinases-2 and 9 were measured. RESULTS: There were 23 subjects in the study, with 13(56.5%) in the supplemented group and 10(43.4%) in the control group. Serum levels of matrix metalloproteinases-2 and tumour necrosis factor alpha were significantly decreased in the supplemented group (p<0.05). After exhaustive exercise, serum levels of matrix metalloproteinases-2, high-sensitivity C-reactive protein and tumour necrosis factor alpha significantly decreased in the supplemented group compared to the control group(p<0.05). CONCLUSIONS: Two-week administration of conjugated linoleic acid reduced the inflammatory factors following exhaustive exercise in young healthy males.

Serum lipid profile in psoriatic patients: correlation between vascular adhesion protein 1 and lipoprotein (a).

Psoriasis is a chronic inflammatory skin disease characterized by excessive cellular replication. Apolipoproteins are genetically determined molecule whose role has been implied in cardiovascular pathology. Vascular adhesion protein-1 (VAP-1) is an adhesion molecule with an enzymatic activity that partakes in the migration process of lymphocytes into sites of inflammation. Our purpose was to evaluate the plasma lipid profiles, apolipoproteins (A1, B) and Lp (a) and VAP-1 in order to compare the lipid profile in psoriatic patients with non-affected persons and correlation between VAP-1 and Lp (a). We determined serum concentrations of lipids, lipoproteins , apolipoproteins and VAP-1 in 90 patients with psoriasis and 90 age matched controls. Serum Lp (a), apo A1 and apo B were measured by immunoprecipitation assays, and the lipids and lipoproteins were measured by enzymatic methods.The VAP-1 were measured by ELISA method. The mean levels of total cholesterol, LDL, apo B and VAP-1 in patients with psoriasis were found to be significantly higher than those of healthy subjects (P<0.05. In psoriatic patients, elevation of VAP-1 correlated with elevation of Lp (a) (p = 0.025). This study shows that high serum lipid level and VAP-1, is significantly more common in psoriasis. This fact may be responsible for higher prevalence of cardiovascular accident in psoriatic patients.

Adipolin and IL-6 Serum Levels in Chronic Obstructive Pulmonary Disease.

Objective(s): One of the adipokines that have insulin-sensitizing properties is adipolin, whose reduced levels have been reported in obesity, oxidative stress, and inflammation. The present study investigated serum interleukin-6 (IL-6) and adipolin levels in chronic obstructive pulmonary disease (COPD) patients. Method: A control case study included 60 COPD patients and 30 healthy subjects in the research and measured adipolin and IL-6 serum levels. In addition, serum adipolin levels in COPD patients were assessed according to the GOLD grade. The relationship between serum adipolin levels and study variables were also analyzed. Results: The results showed reduced adipolin levels in COPD patients compared with healthy individuals (p < 0.001). Furthermore, increased levels of IL-6 were evident in the COPD group compared to the control group (p < 0.001). Adipolin serum levels were positively correlated with PFTs and negatively correlated with IL-6 levels. Conclusion: Decreased adipolin levels enhanced disease severity in COPD patients. It seems that the existence of a significant relationship between adipolin and IL-6 may indicate the role of adipolin in the pathophysiology of COPD.

Crocin attenuates inflammation of lung tissue in ovalbumin-sensitized mice by altering the expression of endoplasmic reticulum stress markers.

Endoplasmic reticulum (ER) stress plays a pivotal role in the pathogenesis of asthma. The present study aimed to investigate the reducing or suppressing effects of crocin in ovalbumin (OVA)-sensitized mice on ER stress markers. Mice were divided into six groups (n = 5 per group) including control, OVA-sensitized (OVA), OVA-treated crocin (OVA-Cr25, OVA-Cr50, and OVA-Cr100 mg/kg), and OVA-treated dexamethasone (1 mg/kg), (OVA-Dexa) groups. Animals 5 later groups were sensitized to OVA and the treatment groups received intraperitoneally crocin/dexamethasone in the last 5 days of the model. At the end of the study, lung tissue was evaluated for airway inflammation, caspase 12 and CHOP protein levels, and expression of ER stress markers using real-time-PCR. Sensitization with OVA significantly caused airway inflammation and induction of ER stress in mice compared to the control group based on the elevated inflammatory cells and ER stress markers in the lung tissue. Treatment with crocin and dexamethasone reduced airway inflammation and suppressed ER stress markers. Interestingly, in the OVA-Cr100 group, the suppressive effects on ER stress apoptotic markers were comparable to the OVA-Dexa group. The results suggest that crocin mediates maladaptive ER stress conditions possibly by creating adaptive ER stress status and driving protein folding correctly.

Pyridine-2,3-dicarboxylate, quinolinic acid, induces 1N4R Tau amyloid aggregation in vitro: Another evidence for the detrimental effect of the inescapable endogenous neurotoxin.

Quinolinic acid (QA) known as a neuro-active metabolite associated with the kynurenine pathway. At high concentrations, QA is often involved in the initiation and development of several human neurologic diseases, like Alzheimer's disease. Because of the QA action as the NMDA receptor, it is considered as a potent excitotoxin in vivo. Since it is probable that different mechanisms are employed by QA, activation of NMDA receptors cannot fully explain the revealed toxicity and it is even believed that there are multiple unknown mechanisms/targets leading to QA cytotoxicity. Herein we report accelerated amyloid oligomerization of 1N4R Tau under the effect of QA, in vitro, then the molecular structure, morphology and toxicity of the protein aggregate were documented by using various theoretical/experimental approaches. The possible mechanism of action of QA-induced Tau oligomerization has also been explored.

Electroactive centers in Euphorbia latex and lentil seedling amine oxidases.

The electrochemical behavior of redox centers in the active site of amine oxidases from lentil seedlings and Euphorbia characias latex was investigated using a mercury film electrode. Tyrosine-derived 6-hydroxydopa quinone (TPQ) and copper ions in the active site are redox centers of these amine oxidases. The enzymes undergo two reduction processes at negative potentials related to the reduction of the TPQ cofactor to the corresponding hydroquinones and the reduction of copper ions, (Cu(II)-->Cu(I)). Copper depleted enzymes, prepared by reduction with dithionite followed by dialysis against cyanide, undergo only one reduction process. Nyquist diagrams, recorded at potentials corresponding to the reduction of cofactors as dc-offset, represent charge transfer impedance followed by a Warburg-type line at low frequencies, indicating the occurrence of a diffusion controlled process in the rate-limiting step of the reduction process.

Combination treatment of all-trans retinoic acid (ATRA) and γ-secretase inhibitor (DAPT) cause growth inhibition and apoptosis induction in the human gastric cancer cell line.

Current medication for gastric cancer patients has a low success rate with resistance and side effects. According to recent studies, γ-secretase inhibitors is used as therapeutic drugs in cancer. Moreover, all-trans retinoic acid (ATRA) is a natural compound proposed for the treatment/chemo-prevention of cancers. The aim of this study was to explore the effects of ATRA in combination with N-[N-(3,5-difluorophenacetyl-l-alanyl)]-S-phenylglycine t-butyl ester (DAPT) as γ-secretase inhibitor on viability and apoptosis of the AGS and MKN-45 derived from human gastric cancer. AGS and MKN-45 gastric cancer cell lines were treated with different concentrations of ATRA or DAPT alone or ATRA plus DAPT. The viability, death detection and apoptosis of cells was examined by MTT assay and Ethidium bromide/acridine orange staining. The distribution of cells in different phases of cell cycle was also evaluated through flow cytometry analyses. In addition, caspase 3/7 activity and the expression of caspase-3 and bcl-2 were examined. DAPT and ATRA alone decreased gastric cancer cells viability in a concentration dependent manner. The combination of DAPT and ATRA exhibited significant synergistic inhibitory effects. The greater percentage of cells were accumulated in G0/G1 phase of cell cycle in combination treatment. The combination of DAPT and ATRA effectively increased the proportion of apoptotic cells and the level of caspase 3/7 activities compared to single treatment. Moreover, augmented caspase-3 up-regulation and bcl-2 down-regulation were found following combined application of DAPT and ATRA. The combination of DAPT and ATRA led to more reduction in viability and apoptosis in respect to DAPT or ATRA alone in the investigated cell lines.

Two-state irreversible thermal denaturation of Euphorbia characias latex amine oxidase.

Thermal denaturation of Euphorbia latex amine oxidase (ELAO) has been studied by enzymatic activity, circular dichroism and differential scanning calorimetry. Thermal denaturation of ELAO is shown to be an irreversible process. Checking the validity of two-state it really describes satisfactorily the thermal denaturation of ELAO. Based on this model we obtain the activation energy, parameter T(*) (the absolute temperature at which the rate constant of denaturation is equal to 1 min(-1)), and total enthalpy of ELAO denaturation. HPLC experiments show that the thermal denatured enzyme conserves its dimeric state. The N(2)-->kD(2) model for thermal denaturation of ELAO is proposed: where N(2) and D(2) are the native and denatured dimer, respectively.

Osmolytic Effect of Sucrose on Thermal Denaturation of Pea Seedling Copper Amine Oxidase.

Protein stability is a subject of interest by many researchers. One of the common methods to increase the protein stability is using the osmolytes. Many studies and theories analyzed and explained osmolytic effect by equilibrium thermodynamic while most proteins undergo an irreversible denaturation. In current study we investigated the effect of sucrose as an osmolyte on the thermal denaturation of pea seedlings amine oxidase by the enzyme activity, fluorescence spectroscopy, circular dichroism, and differential scanning calorimetry. All experiments are in agreement that pea seedlings amine oxidase denaturation is controlled kinetically and its kinetic stability is increased in presence of sucrose. Differential scanning calorimetry experiments at different scanning rates showed that pea seedlings amine oxidase unfolding obeys two-state irreversible model. Fitting the differential scanning calorimetry data to two-state irreversible model showed that unfolding enthalpy and T *, temperature at which rate constant equals unit per minute, are increased while activation energy is not affected by increase in sucrose concentration. We concluded that osmolytes decrease the molecular oscillation of irreversible proteins which leads to decline in unfolding rate constant.

Correlation of serum vascular adhesion protein-1 with airflow limitation and quality of life in stable chronic obstructive pulmonary disease.

OBJECTIVE: The serum vascular adhesion protein-1 (VAP-1) level increases in chronic inflammatory diseases. The present study aimed to examine serum VAP-1 level in patients with stable chronic obstructive pulmonary disease (COPD) and the correlation of this marker with airflow limitation and health-related quality of life using the COPD Assessment Test (CAT). MATERIALS AND METHODS: We measured serum VAP-1 level in 43 patients with stable COPD and 30 control subjects and compared them with airflow limitation according to the COPD stage in the Global Initiative for Chronic Obstructive Pulmonary Disease (GOLD) criteria, peripheral O2 saturation (SpO2), and CAT score. We also tested the association of serum VAP-1 level with COPD patients' clinical parameters. RESULTS: Serum VAP-1 level increased with increasing severity of COPD according to the GOLD classification (P = 0.007). It also increased in patients with high CAT groups and high values on the modified Medical Research Council dyspnea scale (P = 0.012 and P = 0.015, respectively). In addition, there was a significant positive correlation between serum VAP-1 level and both SpO2 and CAT score (r = -0.404, P = 0.007; r = 0.482, P = 0.001, respectively). CONCLUSION: The study showed that serum VAP-1 level increased with an increasing severity of obstruction in patients with stable COPD. This increase was associated with a reduced quality of life and increased severity of hypoxia. These results suggest that inhibiting serum VAP-1 level in COPD patients may be useful in managing the disease.

What can we get from varying scan rate in protein differential scanning calorimetry?

Differential scanning calorimetry has many advantages over other techniques to study the thermal stability of proteins due to its direct measurement of thermodynamic parameters. Most proteins undergo irreversible thermal denaturation causing their thermogram to be scan rate dependent. We modeled reversible and irreversible protein thermograms at varying scan rates. The complete Lumry-Eyring model was used to model the irreversible thermograms at various values of T1/2 (temperature at which equilibrium constant equals unity) and T* (temperature at which rate constant equals 1min-1). Our results have shown that the thermal effects of two processes are integrated with decreasing the T* relative to T1/2. It is also shown that the shape of second derivatives of thermograms under different conditions have specific pattern which can be used to judge and estimate the correct model for protein denaturation.

The status of glycation in protein aggregation.

Protein crucial function and flexibility directly depend on its whole structure which is determined by the native distribution of structural elements. Any disturbances in a protein architecture leads to many kind of abnormalities and intra- or extracellular accumulation of misfolded proteins which are the basis of conformational diseases. Glycation is one of the most important unwanted post-translational modifications (PTM) which modifies protein three dimensional decoration and triggers its abnormalities. In current review, we take a look at the brief history of protein glycation, its mechanism and kinetics, glycation consequences and toxic products and its involvement in protein chemical modification, aggregation amyloids and fibril formation and different mechanisms induced by such alterations.

Ral signaling pathway in health and cancer.

The Ral (Ras-Like) signaling pathway plays an important role in the biology of cells. A plethora of effects is regulated by this signaling pathway and its prooncogenic effectors. Our team has demonstrated the overactivation of the RalA signaling pathway in a number of human malignancies including cancers of the liver, ovary, lung, brain, and malignant peripheral nerve sheath tumors. Additionally, we have shown that the activation of RalA in cancer stem cells is higher in comparison with differentiated cancer cells. In this article, we review the role of Ral signaling in health and disease with a focus on the role of this multifunctional protein in the generation of therapies for cancer. An improved understanding of this pathway can lead to development of a novel class of anticancer therapies that functions on the basis of intervention with RalA or its downstream effectors.

Conformational study of human serum albumin in pre-denaturation temperatures by differential scanning calorimetry, circular dichroism and UV spectroscopy.

Thermal conformational changes of human serum albumin (HSA) in phosphate buffer, 10 mM at pH = 7 are investigated using differential scanning calorimetric (DSC), circular dichroism (CD) and UV spectroscopic methods. The results indicate that temperature increment from 25 degrees C to 55 degrees C induces reversible conformational changes in the structure of HSA. Conformational change of HSA are shown to be a three-step process. Interestingly, melting temperature of the last domain is equal to the maximum value of fever in pathological conditions, i.e. 42 degrees C. These conformational alterations are accompanied by a mild alteration of secondary structures. Study of HSA-SDS (sodium dodecyl sulphate) interaction at 45 degrees C and 35 degrees C reveals that SDS affects the HSA structure at least in three steps: the first two steps result in more stabilization and compactness of HSA structure, while the last one induces the unfolding of HSA. Since HSA has a more affinity for SDS at 45 degrees C compared to 35 degrees C, It is suggested that the net negative charge of HSA is decreased in fever, which results in the decrease of HSA-associated cations and plasma osmolarity, and consequently, heat removal via the increase in urine volume.

Investigation on the surface hydrophobicity and aggregation kinetics of human calprotectin in the presence of calcium.

Calcium and zinc binding protein, calprotectin is a multifunctional protein with broad spectrum antimicrobial and antitumoural activity. It was purified from human neutrophil, using a two-step ion exchange chromatography. Since surface hydrophobicity of calprotectin may be important in membrane anchoring, membrane penetration, subunits oligomerization and some biological roles of protein, in this study attempted to explore the effect of calcium in physiological range on the calprotectin lipophilicity. Incubation of human calprotectin (50 microg/ml) with different calcium concentrations showed that 1-anilino-8-naphthalene sulfonic acid (ANS) fluorescence intensity of the protein significantly elevates with calcium in a dose dependent manner, suggesting an increase in calprotectin surface hydrophobicity upon calcium binding. Our study also indicates that calcium at higher concentrations (6, 8 and 10 mM) induces aggregation of human calprotectin. Our finding demonstrates that the starting time and the rate constant of calprotectin aggregation depend on the calcium concentration.