bijan ranjbar

Zinc oxide quantum dots (ZnO QDs) possess unique optical, electronic, and chemical properties due to the quantum confinement effect, making them ideal for sensing applications. Also, advances in sol-gel synthesis allow precise control over size, shape, and surface chemistry, improving functionality. By adjusting synthesis parameters, their effectiveness in optical and electrochemical applications has been increased. However, further research is needed to understand the relationship between synthesis parameters and performance fully. In this paper, ZnO QDs were synthesized using sol-gel techniques. The synthesis parameters, such as precursor concentrations, pH, temperature, and reaction time, were optimized to control the size, morphology, and properties of the ZnO QDs. The electrochemical characterization of the ZnO QDs was then studied by cyclic voltammetry utilizing K4[Fe(CN)6], as a known electrochemical probe in biosensing, in 0.1 M KCl solution. Also, a blood sample was used to find the electrochemical behavior of the ZnO QDs modified on a glassy carbon electrode (GCE) in a biological matrix. It was found that the modified working electrode, ZnO QDs/GCE, acts as an anti-oxidative in an alkaline blood medium and oxidative in the electrolyte of KCl.

In this study, 50 Staphylococcus aureus samples from Baghdad Hospital were collected and examined, 17 samples were infected with methicillin-resistant Staphylococcus aureus (MRSA) and 5 samples were infected with vancomycin-resistant Staphylococcus aureus (VRSA). The sensitivity of the isolates against different antimicrobial agents was evaluated using the VITEK2 standard system. According to CLSI, the minimum inhibitory concentration (MIC) values of zinc oxide quantum dots (ZnO-QDs) were also tested by the Muller-Hinton dilution method. In addition, polymerase chain reaction (PCR) was performed to identify vanA and mecA genes. The antibacterial effects of ZnO-QDs on VRSA were higher than MRSA isolates.

The study of protein-gold nanoparticles interaction has shown valuable role in medicine, including: drug delivery, vaccine design, biosensors, bioassays, and imaging. Anti-microbial peptides (AMPs) are short amino acid sequences that have important function in the medicinal treatment of multi drug resistant infections. Binding of AMPs to gold nanoparticles (AuNPs) is benefitable for long-term storage, targeted delivery into cells and reduction of drug dosage. This requires preserving the shape and size of the nanoparticles involved in the interaction. In this study, we investigated the interaction of AuNPs in concentration of 2.28 × 10-7 M with three concentrations (0.8, 2, 4 µM) of the antimicrobial peptide Pexiganan in different volumes (2-100µL), in order to study the changes in the shape, charge and size of the particles involved in the interaction by UV-absorption spectroscopy, DLS and transmission electron microscopy (TEM). In all three concentrations, with the increase in peptide concentration  resulted from increasing the volume of peptide solution, the surface charge of the particles became more positive and the size of the particles increased, this was observed in the form of a new peak at the values ​​above 600 nm in the absorption spectrum of AuNPs, which is due to the interaction of the amin Π group of the amino acid lysine in peptide sequence with the surface of nanoparticles. As a result, the aggregation of AuNPs was observed at higher concentrations of peptide.

The human enzyme carbonic anhydrase II (HCA II) is a cytosolic protein located in the membrane of red blood cells, and it is involved in various physiological and pathological processes. It can catalyze the reversible hydration of carbon dioxide efficiently. Given the critical role of the HCA II, computational methods such as molecular dynamics simulation (MD) are used to study the structure and dynamics of the wild-type and the mutant enzymes. Based on the previous experimental studies, mutant enzymes enhance kinetic activity or decrease stability. Before MD, quantum mechanics studies were performed. The native enzyme was in a stable state after MD in terms of potential energy and Gibbs-free energy. As evidenced by RMSD, RMSF, and Rg, One of the mutated enzymes that affect the activity of the enzyme has more stability, less fluctuation, and less Rg than other enzymes. In two other mutants that also affected the stability of the enzyme, compared to the previous two enzymes, lower stability, more fluctuations, and potential energy level were observed, which caused the instability of these enzymes during the simulation. These results can help in the engineering and design of new variants of carbonic anhydrase enzyme.

AbstractA layer of proteins covers the nanoparticles by exposure to the nanoparticles in biological fluids. The phenomenon known as biocorona can alter the nanoparticle's specific purpose. Since the usage of nanoparticles in biological issues such as drug delivery, biosensor, and photothermal has increased, evaluating nanoparticles' interactions with biomolecules is necessary. Hydrophilic polymers form a layer of water molecules that reduces the interaction potential between nanoparticles and biomolecules. In this study, the effects of gold nanoparticle morphology (spheres and rods) and surface functionalization (PEG and GSH) on glycosylated serum albumin, a model protein in diabetic patients, its secondary structure and chemical stability using circular dimorphism technique were investigated.PEG-AuNPs exhibit a larger hydrodynamic radius than GSH-AuNPs due to their large hydrophilic tails. After interaction with the protein, the nanoparticles showed less interaction with the protein due to the formation of a layer of water around them that reduces the probability of interaction with proteins. The circular dichroism also exhibits that different modified nanoparticles do not significantly influence secondary structure. The presence of nanoparticles with hydrophiliccoatings, mainly polyethylene glycol with high water retention, reduce protein availability from urea in the long run and as a result will increase the 〖∆G〗_H2O value.

A layer of proteins covers the nanoparticles by exposure to the nanoparticles in biological fluids. The phenomenon known as biocorona can alter the nanoparticle's specific purpose. Since the usage of nanoparticles in biological issues such as drug delivery, biosensor, and photothermal has increased, evaluating nanoparticles' interactions with biomolecules is necessary. Hydrophilic polymers form a layer of water molecules that reduces the interaction potential between nanoparticles and biomolecules. In this study, the effects of gold nanoparticle morphology (spheres and rods) and surface functionalization (PEG and GSH) on glycosylated serum albumin, a model protein in diabetic patients, its secondary structure and chemical stability using circular dimorphism technique were investigated.PEG-AuNPs exhibit a larger hydrodynamic radius than GSH-AuNPs due to their large hydrophilic tails. After interaction with the protein, the nanoparticles showed less interaction with the protein due to the formation of a layer of water around them that reduces the probability of interaction with proteins. The circular dichroism also exhibits that different modified nanoparticles do not significantly influence secondary structure. The presence of nanoparticles with hydrophiliccoatings, mainly polyethylene glycol with high water retention, reduce protein availability from urea in the long run and as a result will increase the 〖∆G〗_H2O value.

Spectral properties and thermal stability of AS1411 G-quadruplex AS1411 is an anticancer four-stranded deoxyoligonucleotide with high affinity and specificity to a putative surface biomarker, nucleolin, which is an overexpressed protein on numerous cancer cells. AS1411 has valuable functional potential for the targeted delivery of nanoparticles, oligonucleotides, peptides and small drug molecules to cancer cells. Considering that understanding interaction of drug with target molecule is important and necessary for pharmaceutical studies, in the present study, the interaction of a porphyrin photosensitizer called TMPYP4 was evaluated with aptamer AS1411. Absorption and fluorescence spectroscopy and circular dichroism technique were used to identify how and where TMPYP4 binds to AS1411 and the resulting structural changes. The results showed that binding of the porphyrin to AS1411 caused 13 nm red shift and 56% hypochromicity in the absorption spectrum; in addition, due to this binding, the emission spectrum of porphyrin is changed and its emission intensity is reduced. The results of structural studies showed that the binding of TMPYP4 does not significantly change the shape of the AS1411 circular dichroism spectrum, but at high concentrations leads to an intense decrease in the intensity of the spectrum. These changes in the spectra indicate that TMPYP4 binds to the aptamer through intercalation between tetrad planes and end-staking and causes to opening of the aptamer structure. As a conclusion, it can be proposed that AS1411 aptamer has appropriate potential for delivery of porphyrin compounds and their photosensitizer types and can be used in photodynamic therapy of cancer cells.

It is well known that many biomolecules are chiral and their structure can be monitored by chiroptical spectroscopy. Nevertheless, their analysis in the natural environment of biofluids remains challenging. Recently, little efforts have been made to study biofluids by chiroptical techniques and find a specific signature for healthy/diseased conditions. Blood plasma can be a great subject for this line of examinations. In this study real clinical human blood plasma samples from 46 subjects were analyzed using CD spectropolarimetry to discriminate between type 2 diabetic patients and the control group. For more a challenging condition, patients were selected with type 2 diabetic and ulcer. The results showed a significant decrease in the total α-helical conformation of plasmatic proteins obtained from patients. Also total plasmatic protein content varied with disease condition. As a result, circular dichroism was useful to discriminate between the diabetic patients and the control group, and even between the diabetic patients with or without ulcer. Results of this study encourage possibility of using this technique as a useful supportive tool to conventional diagnostic methods.

Gold nanoparticles are promising materials for biomedical applications because of the attractive optical properties such as the absorption and scattering of light at resonant wavelength. Due to the fruitful applications of gold nanoparticles (GNPs), they are appropriate for a variety of biological studies. One of the most important applications of nanoparticles is protein carriers, in which transport of therapeutically relevant protein is done to in vivo or in vitro targets. Protein folding and properties of probable intermediates during the folding of proteins had been investigated in several studies. The molten globule state, a main intermediate of protein folding, has native-like secondary but perturbation of tertiary structure. Consequently, the influence of gold nanoparticles concentration on a model protein was studied by far- and near-UV circular dichroism (CD), Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), intrinsic fluorescence emission spectroscopy and 8-Anilino-1-naphthalenesulfonic acid binding. The results indicated that the interactions between gold nanoparticles and lysozyme lead to the formation of molten globule-like state.

Human alpha1-antitrypsin is a glycoprotein comprised of 394 amino acids and 52 kDa molecular weight, which is mostly synthesized and secreted by hepatocytes, diffuses to interstitial lung tissues, and has an essential function to protected tissues against neutrophil elastase. One of the significant challenges in dealing with alpha-1-antitrypsin is the structural instability of the folded form of protein and, consequently, the accumulation of polymers in lung tissue. This makes patients vulnerable to chronic obstructive pulmonary disease, severe asthma, and emphysema. Intravenous augmentation therapy of alpha 1-antitrypsin is one of the most prevalent therapies. Moreover, patients who are candidates for that have respiratory symptoms, and the use of bronchodilator (Salbutamol) is the first recommended standard treatment. In this study, protein purification was performed by using high-performance affinity chromatography and, its purity was confirmed by gel electrophoresis. The effect of different concentrations of salbutamol on heat-induced polymerization at 60 ° C was investigated by non-denaturing polyacrylamide gel electrophoresis, dynamic light scattering (DLS), and circular dichroism (CD) techniques. Protein activity was measured by trypsin inhibitor capacity (TIC) assay. The results indicated that salbutamol decreases the rate of polymerization by reducing the flexibility of the reactive center loop, thus decelerate protein activity reduction. Therefore, salbutamol can be an appropriate supplementary for alpha 1-antitrypsin and a proper option for the treatment of protein polymerization associated diseases.

Aptamers, DNA or RNA single-stranded sequences, have different applications in biological investigations, such as apatsensors, due to their many advantages including high specificity and affinity, cost-effectiveness and easy synthesis. In this study, an aptasensor was designed based on the changes in the SPR spectra of gold nanoparticle, in order to detect carcinoembryonic antigen (CEA) cancer indicator as a marker for breast cancer. In the presence of aptamer, gold nanoparticles were stable, SPR spectrum of gold nanoparticle was unchanged after adding NaCl. However, in the presence of CEA as a cancer marker, aptamer binds to the target molecule and by adding NaCl consequently the SPR spectrum of gold nanoparticles is changed. The results of this study showed that the designed aptasensor enables the detection of CEA over a range of 50 ng ml-1. The limit of detection was about 22.75 ng ml-1. It seems this aptasensor can be used in detection of carcinoembryonic antigen cancer marker.

Gold nanoparticles are promising materials for biomedical applications because of the attractive optical properties such as the absorption and scattering of light at resonant wavelength. Due to the fruitful applications of gold nanoparticles (GNPs), they are appropriate for a variety of biological studies. One of the most important applications of nanoparticles which consist of transport of therapeutically relevant protein to in vivo or in vitro targets is protein carriers. Protein folding and properties of probable intermediates during the folding of proteins had been investigated in several studies. The molten globule state, a main intermediate of protein folding, has native-like secondary but perturbation of tertiary structure. Consequently, the influence of gold nanoparticles concentration on a model protein was studied at the buffer concentration by far- and near-UV circular dichroism (CD), Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), intrinsic fluorescence emission spectroscopy and 8-Anilino-1-naphthalenesulfonic acid binding. The results indicated that the interactions between gold nanoparticles and lysozyme lead to the formation of molten globule-like state.

Circular dichroism spectroscopy is a simple way to study G-quadruplex structure and is very useful for monitoring the conformational changes in G-quadruplex structure induced by modifications of the environment. Plasmonic nanoparticles with localized surface plasmon resonance (LSPR) can create strong electromagnetic fields at the surface of plasmonic metals, which remarkably influence the optical properties of molecules. Plasmonic CD is a new CD signal which originates from the dipole–dipole interactions between surface plasmons of NPs and chiral biomolecules have received interest research in various fields of nanotechnology. In this paper we study the interaction between gold nanorods (GNR) and two types of G-quadruplex (parallel and antiparallel), to monitor the alterations in DNA conformation and plasmonic CD signal upon formation of GNR-quadruplex nanobioconjugate. The results from this study indicate the plasmonic CD signals in visible regions are more sensitive than Far-UV CD signals to detect the spatial conformational state of G-quadruplex-GNR nanobioconjugate.

Prostate cancer is one of the most prevalent cancer in men which shows high heterogeneity in genetic and pathological features. Elucidating the regulatory relationships between microRNAs and mRNAs can help to identification of gene regulatory patterns in metastatic prostate cancer.
In the present study prostate cancer patient’s expression data (gene and microRNA) was used to study gene interactions in metastatic prostate tumor. Weighted gene co-expression network have been implemented for gene clustering and finding gene modules correlation with biochemical recurrence free survival variable. Differentially expressed microRNA gene targets were obtained from experimentally validated and prediction based databases and alongside with gene and microRNA expression, Pearson correlations measurements were implemented to constructing microRNA regulatory network.
Two significant modules were detected in co-expressed modules significant analysis for biochemical recurrence free variable. One of them involved in cell cycle regulation and cell proliferation pathways which are hallmark pathways of progressed cancers. Integration of gene co-expression network with microRNA regulation network shows, first: Micrornas target pathways which involved in the progression of prostate cancer to metastatic stage, and second: introduce several key factors including microRNA and genes.
Present study revealed more details on key functional components in prostate cancer development. These details may provide opportunities for the development of alternative therapeutic approaches.

The Cu dependent restriction deoxyribozyme is the unique example of known deoxyribozymes. The uniqueness of this deoxyribozyme is originated from specific cleaving of single stranded DNA and formation of triple helix DNA structure which is necessary for substrate recognition and binding. The most established method for measuring the kinetic parameters of deoxyribozyme is based on use of radiolabeled substrates which have several difficulties. In this study we present accurate, fast and inexpensive methods for kinetic study of the deoxyribozyme which is based on extrinsic fluorescence and UV-visible spectroscopy techniques. As mentioned above, DNA triple helix formation is necessary for substrate identification and also enzyme activity. Circular dichroism spetropolarimetery is used for structural study of enzyme. Analysis of spectrum results from this technique indicates structural changes which is a direct evidence for the triple helix formation in enzyme-substrate complex. Extrinsic fluorescence experiment is based on high affinity of SYBR gold to double stranded DNA compared to single stranded DNA. Enzyme activity can be measured by SYBR gold fluorescence emission upon addition of cofactor to the enzyme-substrate complex. Continuous hyperchromicity assay method which is based on UV-visible spectroscopy was used for measuring of enzyme activity by hyperchromicity of the enzyme-substrate complex after addition of cofactor. Comparison of the results show that the continuous hyperchromicity assay is more accurate than the extrinsic fluorescence method, because of this method is based on intrinsic physicochemical properties of DNA without interference of external factors.

Current study is aimed at designing and producing gold-nanoparticle based aptasensor for colorimetric detection of tri-nitro toluene (TNT).
Gold-nanoparticles have a wide range of application in designing biosensors for their special and highly sensitive plasmonic characteristics. In the present study, TNT molecule has been detected by designing and producing gold nanoparticle based aptasensor. After synthesizing gold nanoparticles and functionalizing them by ssDNA aptamer having 52 nucleotides, aptasensor performance for detecting target molecule was evaluated. Techniques such as dynamic light scattering (DLS), transmission electron microscope and UV-Vis spectrophotometer were used to characterize the size and shape of nanoparticles, functionalizing them by aptamer, and also their sensitivity to detect target.
UV-Vis spectrophotometer, DLS, and TEM microscopy tests indicated that gold nanoparticles were synthesized with excellent quality and average size of 40 nm. TNT molecule was colorimetric detected with sensitivity of 15 nanomolar using gold nanoparticle based aptasensor.
According to the results it can argue that the strategy promises a novel method in detection due to wide range of such aptasensors detection. .

The aging process is related to some functional changes of the tissues and cells, including cell membrane. Erythrocytes, are among the most suitable biological models to study the effect of aging on cell function, as they have no nuclei and other organelles. Moreover, any alterations of erythrocytes are accompanied by changes in absorbance detection in UVvisible emission. Also, the biophysical properties of the erythrocyte membrane skeleton proteins and hemoglobin, play important roles in deformability of erythrocytes. Furthermore, the erythrocytes’ deformability and aggregation declines and increases respectively, during aging process. Also hemoglobin affinity to oxygen increases and oxygen release to the tissues decreases in aging process. Therefore in this report the effect of age on structural and thermodynamical changes of erythrocyte membrane skeleton proteins and hemoglobin in mature rats are studied by different spectroscopy methods like circular dichroism (CD), FTIR, UV-Visible and differential scanning calorimetry (DSC). The results showed that aging of the rats’ erythrocytes leads to the compactness of erythrocytes membrane skeletal proteins structure. Thus, the reduction in erythrocytes flexibility and increment in the compactness and rigidity of the hemoglobin structure occur. Accordingly, these changes result in more severe iron binding to oxygen and decrease in oxygen delivery to the tissues.

Haemophilus influenzae type b (Hib) is the leading cause of bacterial meningitis, otitis media, pneumonia, cellulitis, bacteremia, and septic arthritis in infants and young children. The Hib capsule contains the major virulence factor, and is composed of polyribosyl ribitol phosphate (PRP) that can induce immune system response. Vaccines consisting of Hib capsular polysaccharide (PRP) conjugated to a carrier protein are effective in the prevention of the infections. However, due to costly processes in PRP production, these vaccines are too expensive..
To enhance biomass, in this research we focused on optimizing Hib growth with respect to physical factors such as pH, temperature, and agitation by using a response surface methodology (RSM)..
We employed a central composite design (CCD) and a response surface methodology to determine the optimum cultivation conditions for growth and biomass production of H. influenzae type b. The treatment factors investigated were initial pH, agitation, and temperature, using shaking flasks. After Hib cultivation and determination of dry biomass, analysis of experimental data was performed by the RSM-CCD..
The model showed that temperature and pH had an interactive effect on Hib biomass production. The dry biomass produced in shaking flasks was about 5470 mg/L, which was under an initial pH of 8.5, at 250 rpm and 35° C..
We found CCD and RSM very effective in optimizing Hib culture conditions, and Hib biomass production was greatly influenced by pH and incubation temperature. Therefore, optimization of the growth factors to maximize Hib production can lead to 1) an increase in bacterial biomass and PRP productions, 2) lower vaccine prices, 3) vaccination of more susceptible populations, and 4) lower risk of Hib infections..

Lipases, as an important enzyme group, are able to catalyze hydrolysis or synthesis of esters.The lipase from pseudomonas fluorescens (E.C.3.1.1.3) is a thermophilic kind of lipases (MW around 33 Kd).
In this study, the effect of different concentrations of sorbitol on the activity and conformational stability of Psedomonas fluorescence lipase was evaluated using UV/Vis and Circular Dichroism (CD), respectively. According to the results of thermodynamic studies the 0.6 M concentration of sorbitol was selected for refolding and unfolding kinetic measurements with stopped flow fluorescence apparatus. Kinetics data indicate that unfolding of lipase is performed via two different pathways; one of them is probably involves a synchronous unfolding and dissociation of subunits and the other one comprises a two step unfolding in which the subunits are first dissociated followed by complete unfolding of subunits. We found that more population of protein molecules unfolded with slow phase unfolding pathway when sorbitol is present in the unfolding buffer. Furthermore; refolding kinetics data suggest that in the presence of sorbitol the energy barrier of refolding is reduced.

Acute Myocardial Infarction AMI is one of the leading causes of death throughout the world. Usual methods for detecting AMI are expensive, time-consuming and using blood samples as biological samples. Therefore, creating an ultra-fast, sensitive and non-invasive diagnostic test is necessary. Herein, a novel ultra-sensitive, fluorescent, plasmon-exciton coupling hybrid of a Gold Nano Rod-Quantum Dot RQ -based aptamer nanobiosensor is presented for the detection of human cardiac troponin I cTnI, the golden biomarker of AMI, and a preclinical test is performed with saliva. The binding of the cTnI protein to aptamer leads to a fluorescence enhancement of the plexcitonic hybrid system. The limit of detection of this nanobiosensor is 0.5 fM. It seems this novel nanobiosensor of the RQ plexcitonic hybrid system can open up new opportunities for the design and fabrication of nanobiosensor progress in nanobiotechnology.

Bacillus subtilis lipase A is the smallest member of α/β hydrolase family with no interfacial activation property. Bacillus subtilis lipase A has numerous applications as well as other lipases، such as industrial، pharmaceuticals، environmental and food products. There have been presented several reports about the engineering of this enzyme based on the random mutagenesis. Therefore، study of molecular dynamics simulation of the enzyme at different temperatures seems to be necessary to understand its dynamical properties. Understanding of such molecular motions is important to switch from random to rational design of the enzyme. Two flexible loops have been identified based on 15 ns molecular dynamics simulation of the enzyme. The extent of flexibility for the loops was different at three temperatures. On the other hand، two critical loops have been identified to play important role on the functional motions of the enzyme as hinges of the axial motions of the secondary elements around the active site cleft.

DNA molecules contain nitrogenous bases that look like fluorophores; however they are weakly or non-fluorescent. Hence، it is important to identify DNA binding-ligands that do not show fluorescence emission in the Free State، though their fluorescence intensity increases upon binding to DNA. Here،we report metal ions (either K and Na) induced guanine quadruplex formation with PS2. M، d (GTG3TAG3CG3T2G2)، which shows peroxidase function when complexed with hemin. Ultravioletvisible absorption spectroscopy revealed activity of the PS2. M oligomer as DNAzyme، and Circular Dichroism spectroscopy showed the formation of G-quadruplex structure of PS2. M. We also studied the intrinsic fluorescence of G-quadruplex forming peroxidase-like DNAzyme. The fluorescence spectra showed increment in the intrinsic fluorescence of folded DNA in comparison with its unfolded structure of the same sequence. Moreover، unsymmetrical cyanine dye (SYBR gold) was utilized as a probe for the study of the extrinsic fluorescence of G-quadruplex DNA، where it could discriminate between the single and four-stranded structures of DNA. Also the G-quadruplex dye interaction was also investigated using Circular Dichroism and Fluorescence spectroscopies.

The stability of enzymes with no reduction in their catalytic activity still remains a critical issue in industrial applications. Naturally occurring osmolytes are commonly used as protein stabilizer. Apart from increasing the stability and catalytic activity، these osmolytes do not change the structure of enzyme. There are a few general schemes about the stabilization mechanism of these osmolytes but the details of their mechanism have not been found so far. In this study، we investigated the simultaneous effects of sorbitol and trehalose on the activity and structural stability of Pseudomonas cepacia lipase (PCL) using UV–visible، fluorescence and circular dichroism (CD) spectroscopy. In order to trace the refractive index and dielectric constant alterations upon the addition of osmolytes، microenvironment of the enzyme (PCL) was studied by means of SPR technique. The results revealed that osmolytes increased catalytic activity and intrinsic fluorescence intensity of PCL. In the presence of both osmolytes the activity of enzyme is greater than when each of the osmolytes is used individally. Far-UV CD spectra indicated that the secondary structural content of protein has been some what increased upon interacting with these osmolytes. The results of SPR technique indicated none of the above osmolytes could change the dielectric constant of medium considerably. This study revealed the synergy of two osmolytes toward increasing the activity and stability of enzyme.

Selection of a system for successful recombinant protein production is important. The aim of this study was to produce high levels of human interleukin-2 (hIL-2) in soluble form. To this end, the pET32a vector in Escherichia coli BL21 (DE3) was used as an expression system, since it was previously used for the production of mouse IL-2 in soluble form. The results indicated that contrary to expectations, the expressed protein was in the form of inclusion bodies and perhaps amino acid differences between human and mouse IL-2 should be determinant. The hIL-2 protein is a small peptide, therefore its recovery as a biologically functional protein by the process of refolding may be feasible and could lead to high yields at the industrial scale.