Polar Amino Research Articles

Diacetyl strategy for synthesis of NHAc containing glycans: enhancing glycosylation reactivity via diacetyl imide protection.

The presence of NHAc groups in the substrates (both glycosyl donors and acceptors) significantly reduced the reactivity of glycosylation. This decrease was attributed to the NHAc groups forming intermolecular hydrogen bonds by the NHAc groups, thereby reducing molecular mobility. Hence, a diacetyl strategy involving the temporary conversion of NHAc to diacetyl imide (NAc2) was developed for the synthesis of NHAc-containing glycans. This strategy has two significant advantages for oligosaccharide synthesis. The NAc2 protection of NHAc substantially enhances the rate of glycosylation reactions, resulting in improved yields. Moreover, NAc2 can be readily reverted to NHAc by the simple removal of one acetyl group under mild basic conditions, obviating the necessity for treating the polar amino group. We have achieved the efficient synthesis of oligosaccharides containing GlcNHAc and N-glycans containing sialic acid using the diacetyl strategy.

Preparation and application of a novel imine-linked covalent organic framework@silica composite for reversed-phase and hydrophilic interaction chromatographic separations

The composites of covalent organic frameworks (COFs) and silica gel have been considered to be promising chromatographic separation materials due to the distinct advantages such as large specific surface area, good mechanical strength and high porosity. In the present study, a novel imine-linked COF@silica composite was prepared by in-situ growth of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) and 2,5-dihydroxyterephthalaldehyde (DHTA) monomers on the surface of aminated silica gel (SiO2–NH2). The successful surface-modification of TAPT-DHTA-COF distinctly enhanced the separation selectivity and efficiency of SiO2–NH2. Multiple types of analyte-stationary phase interactions contributed to the selective retention of structurally similar analytes. The designed TAPT-DHTA-COF@SiO2 was observed to effectively separate hydrophobic phenyl ketones, phthalate esters and steroid hormones. Moreover, the polar amino and hydroxyl groups of TAPT-DHTA-COF facilitated the selective determination of hydrophilic nucleosides/bases. The kinetic performance and thermodynamic behavior of TAPT-DHTA-COF@SiO2 column were particularly explored. It was found that column efficiency was mainly affected by the mass transfer resistance, and the retention of nucleosides/bases on the TAPT-DHTA-COF@SiO2 column was temperature dependent. The developed versatile TAPT-DHTA-COF@SiO2 column was finally applied for detecting environmental hormones as well as water-soluble nicotinamide in real samples. In summary, the potential application of TAPT-DHTA-COF@SiO2 composite material for liquid chromatographic separations was first explored and verified. The TAPT-DHTA-COF@SiO2 was proved to be a promising chromatographic separation material.

Manipulating the Thermal Conductivity of the Graphene/Poly(vinyl alcohol) Composite via Surface Functionalization: A Multiscale Simulation.

The reverse non-equilibrium molecular dynamics simulation is used to investigate the influence of functional groups (FGs) on the thermal conductivity of a graphene/poly(vinyl alcohol) (PVA) composite, which considers non-polar (methyl) and polar (hydroxyl, amino, and carboxyl) groups. First, the polar groups can be more effective to improve the interfacial thermal conductivity than the non-polar group. This can be explained well by characterizing the interfacial Coulombic energy, number and lifetime of hydrogen bonds, vibrational density of states, and integrated autocorrelation of the interfacial heat power. Moreover, the hydroxyl group can improve the interfacial thermal conductivity more than the other groups, which can be rationalized by analyzing the surface roughness of graphene and the radial distribution function of FGs and the PVA chains. However, the introduction of FGs destroys the graphene structure, which consequently reduces the intrinsic thermal conductivity. Furthermore, by adopting the effective medium approximation model and finite element method, there exists a critical graphene length where the overall thermal conductivities are equal for the functionalized and pristine graphene. Finally, the distribution state of graphene is emphasized to be more vital in determining the overall thermal conductivity than the generally accepted interfacial thermal conductivity.

Optimizing the dielectric and mechanical properties of melamine based‐benzoxazine resin by copolymerizing with epoxy resin

AbstractBenzoxazine resins are suffering from high curing temperature, low crosslinking density, and poor toughness, which hampers their broad applications. The introduction of melamine during synthesis has been shown useful in improving these properties, but the dielectric property was deteriorated heavily. Epoxy resins show higher crosslinking density and better toughness but the thermal properties are relatively poor. Herein, the melamine based‐benzoxazine MBF was copolymerized with epoxy resin E51 in this work in order to improve the dielectric properties. The curing reactivity, polymerization mechanism and the comprehensive properties such as thermal, dielectric and mechanical properties were systematically verified. It is found that the abundant active functional groups such as amino and phenolic groups in MBF could catalyze and copolymerize with E51 and form uniform copolymers poly(MBF‐E) at various proportions. With the increasing of epoxy resins, more polar amino groups was consumed, thus the polarity and the water absorption of the copolymers decreased. Additionally, the dielectric constant decreased from 3.67 for poly(MBF) to 2.94 for poly(MBF‐60E). Meanwhile, the highest increasement of tensile strength and elongation at break value reached 130% and 70%, respectively, which may be caused by the higher crosslinking density and more flexible ether bond formed.

Novel amino analogs of the trimethoxyphenyl ring in potent colchicine site ligands improve solubility by the masked polar group incorporation (MPGI) strategy

The low aqueous solubility of colchicine site antimitotic agents, of which the trimethoxyphenyl (A ring) is a heavy contributor, is a serious drawback in their clinical development. We have designed new A ring analogs with chameleonic masked polar amino groups able to increase aqueous solubility and also behave as non-polar through intramolecular hydrogen bonds when bound to tubulin. We have incorporated these new A rings in several scaffolds (sulfonamides, combretastatins, phenstatins, isocombretastatins), synthesized, and assayed 43 representatives. The amino analogs show improved aqueous solubility and some of them (8, 60Z, and 67) nanomolar anti-proliferative potencies against human cancer cell lines, with the most favorable substituent being a 3-methylamino group. The antiproliferative effect relates to tubulin inhibition as shown by in vitro tubulin polymerization inhibition, immunofluorescence microscopy, and cell cycle and apoptosis analysis by flow cytometry. The compounds arrest the cell cycle of treated cells in G2/M and later develop an apoptotic response. Docking studies suggested binding at the colchicine site of tubulin with good agreement with the DFT models of the new structural variations made. The 3-methylamino-4,5‑dimethoxyphenyl moiety is an example of the masked polar group incorporation (MPGI) strategy for soluble ligands binding to hydrophobic sites and a good trimethoxyphenyl ring replacement for the development of new colchicine site ligands.

Engineering of biomimetic mineralized layer formed on the surface of natural dental enamel

The problem of engineering a biomimetic mineralized layer on the surface of native dental tissue (bio-template) was considered in our work.The formation of the mineralized layer on a biotemplate is achieved with the use of nanocrystalline carbonate-substituted calcium hydroxyapatite (HAp), calcium alkali, and a complex of polyfunctional organic and polar amino acids.By applying the set of structural and spectroscopic methods of analysis we have confirmed the formation of a mineralized biomimetic HAp layer on the surface of bio-template with properties resembling those of natural hard tissue. The thickness of the biomimetic mineralized layer varies from 300 to 500 nm, while the direction of some ncHAp nanocrystals coincides with that of the apatite crystals in the enamel.We also demonstrated that the engineered mineralized HAp layer was characterized by homogeneous micromorphology and enhanced nanohardness in the region of the enamel rods exceeding those of native enamel.The development of a strategy for biomimetic engineering and a technique for enamel surface pre-treatment to enable tissue mineralization has huge potential in dental applications.

Unusual Size Effect in Ion and Charge Transport in Micron‐Sized Particulate Aluminum Anodes of Lithium‐Ion Batteries

Aluminum is a promising anode material for lithium-ion batteries owing to its high theoretical capacity, excellent conductivity, and natural abundance. An anomalous size effect was observed for micron-sized aluminum powder electrodes in this work. Experimental and theoretical investigations reveal that the insulating oxide surface layer is the underlying cause, which leads to poor electrical conductivity and limited capacity utilization when the particle is too small. Additionally, poor electrolyte wettability also accounts for the hindered reaction kinetics due to the weak polarity feature of the oxide layer. Surface grafting of polar amino groups was demonstrated to be an effective strategy to improve electrolyte wettability. The present work revealed the critical limitations and underlying mechanisms for the aluminum anode, which is crucial for its practical application. Our results are also valuable for other metallic anodes with similar issues.

Unusual Size Effect in Ion and Charge Transport in Micron‐Sized Particulate Aluminum Anodes of Lithium‐Ion Batteries

AbstractAluminum is a promising anode material for lithium‐ion batteries owing to its high theoretical capacity, excellent conductivity, and natural abundance. An anomalous size effect was observed for micron‐sized aluminum powder electrodes in this work. Experimental and theoretical investigations reveal that the insulating oxide surface layer is the underlying cause, which leads to poor electrical conductivity and limited capacity utilization when the particle is too small. Additionally, poor electrolyte wettability also accounts for the hindered reaction kinetics due to the weak polarity feature of the oxide layer. Surface grafting of polar amino groups was demonstrated to be an effective strategy to improve electrolyte wettability. The present work revealed the critical limitations and underlying mechanisms for the aluminum anode, which is crucial for its practical application. Our results are also valuable for other metallic anodes with similar issues.

L-Arginine and l-lysine retard aggregation and polar residue modifications of myofibrillar proteins: Their roles in solubility of myofibrillar proteins in frozen porcine Longissimus lumborum

This study investigated the ability of l-arginine and l-lysine to inhibit the adverse effects of freezing on the structure and solubility of myofibrillar proteins extract (MPE) in porcine Longissimus lumborum. The results showed that freezing decreased solubility of MPE, band densities of actin and myosin heavy and light chains, fluorescence intensity, and contents of free amino group and total sulfhydryls, but increased content of carbonyl groups and absolute zeta-potential of MPE. l-Arginine and l-lysine effectively alleviated the adverse effects of freezing. l-Arginine and l-lysine significantly increased β-sheet content, Tmax1 and ΔH1, but decreased α-helix content and disulfide bond content in MPE. Additionally, the SDS-PAGE analysis showed that l-arginine and l-lysine could prevent appearance of bands at about 150 kDa. Overall, this study shows that both l-arginine and l-lysine could not only abate the aggregation and disruption of MPs, but also reduce the oxidation of their polar amino groups, which ultimately contribute to their superior solubility. The results may be interesting in meat industry.

Simultaneously suppressing the dendritic lithium growth and polysulfides migration by a polyethyleneimine grafted bacterial cellulose membrane in lithium-sulfur batteries

Owing to the ultrahigh theoretical energy density and low-cost, lithium-sulfur (Li-S) batteries hold broad prospects as one of the promising substitutes for commercial lithium-ion batteries. The polysulfides shuttling originated from sulfur cathode and the lithium dendrite growth from lithium anode are the main challenges that hinder the commercial survival of Li-S batteries. Herein, thermal stable bacterial cellulose (BC) separator is successfully fixed with polyethyleneimine (PEI) by a scalable chemical grafting. The hydroxyl groups and amino groups in PEI grafted BC (PEI@BC) separator can participate in the formation of Li2O and Li3N, respectively, contributing to robust solid electrolyte interface with high ionic conductivity. Therefore, the lithium deposition is well regulated, resulting in a spherical and dendrite-free Li deposit pattern. The Li/Li symmetrical cell assembled with PEI@BC separator exhibits excellent cyclic stability, which can continuously plate/stripe for more than 820 h with an overpotential of ∼ 40 mV at 2 mA cm−2. Meanwhile, the polar amino group can restrain the polysulfides migration via chemosorption. As a consequence of these merits, ultrahigh initial capacity (1402 mAh g−1 at 0.1C) and excellent rate performance (440.5 mAh g−1 at 2C) for Li-S full cell are achieved, presenting new insights into the fabrication of multifunctional separators for Li-S batteries.

High-efficiency capture of ammonia using hierarchically porous Zr-MOF nanoarchitectures under ambient conditions: Thermodynamics, kinetics, and mechanisms

Zirconium-based metal–organic frameworks (Zr-MOFs) have emerged as a promising candidate for efficiently eliminating toxic chemicals under ambient conditions. Herein, we demonstrate the remarkable ammonia capture capabilities of the hierarchically porous MOF-808 xerogel (G808) macrostructure and its amino-functionalized analogue (G808-NH2), which were constructed through a sol–gel-based strategy combined with convenient ambient pressure drying. Static isotherm measurements and dynamic breakthrough tests using engineered Zr-MOF xerogel granules were conducted to illuminate the thermodynamic and kinetic characteristics for ammonia sorption. The G808 and G808-NH2 xerogels manifest substantially higher ammonia uptake, intensified interfacial interactions, and enhanced irreversible retention toward ammonia compared with the state-of-the-art activated carbon-based materials, particularly at the low-concentration region. Moreover, these hierarchical Zr-MOF nanoarchitectures exhibit extraordinary ammonia removal performance as well as excellent environmental robustness under simulated respirator canister/protection filter circumstances, with the breakthrough capacities of G808-NH2 being individually more than two and one orders of magnitude greater than those for the pristine and metal-amine impregnated carbons. The kinetic ammonia adsorption behaviors can be well delineated by the pseudo-first-order Wheeler-Jonas model. An in-depth discussion on the ammonia sorption regime, detailing five binding patterns besides reversible physisorption with a special focus on the impacts of polar amino groups and humidity, was proposed based on multiple characterizations and Grand Canonical Monte Carlo simulation.

UV-triggered self-healing SiO2/PDA hybrid microcapsules with both enhanced UV-shielding ability and improved compatibility for epoxy resin coating

UV-triggered single-microcapsule self-healing materials have significant potential in effectively repairing microcracks and improving the reliability of polymer coatings on spacecraft with the aid of abundant UV radiation in space. Unfortunately, UV light can also cause undesirable curing of the repair agent within the microcapsules before self-repairing and make the latent UV-cured healing agent fail. Herein, we developed UV-triggered self-healing SiO2/polydopamine (PDA) hybrid microcapsules with enhanced UV-shielding ability and compatibility for epoxy resin coating. The microcapsules contain a liquid core of mixed epoxy resin (E-51 and A1815) and UV initiator (PI6992) and a novel UV-shielding SiO2/PDA hybrid shell with uniform embedment of an ultrathin PDA layer into the SiO2 mesoporous structure of the shell. As a UV absorber, PDA endows SiO2/PDA hybrid microcapsules with a UV-shielding hybrid shell and protects the core material from undesirable UV-cured behavior before self-repairing in space with abundant UV radiation. In addition, PDA containing benzene rings and polar groups, including hydroxyl, amino, and carbonyl groups, can enhance the compatibility of SiO2/PDA hybrid microcapsules with epoxy resin containing benzene rings and epoxy and hydroxyl groups due to π-π stacking interactions between abundant benzene rings and hydrogen bonding interactions between these polar groups. The epoxy coatings containing SiO2/PDA microcapsules aged for 192 h under UV irradiation maintained great self-repairing ability, which was attributed to the enhanced UV-shielding ability and compatibility.

Thermodynamics of hydrophobic-polar model proteins on the face-centered cubic lattice.

The HP model, a coarse-grained protein representation with only hydrophobic (H) and polar (P) amino acids, has already been extensively studied on the simple cubic (SC) lattice. However, this geometry severely restricts possible bond angles, and a simple improvement is to instead use the face-centered cubic (fcc) lattice. In this paper, the density of states and ground state energies are calculated for several benchmark HP sequences on the fcc lattice using the replica-exchange Wang-Landau algorithm and a powerful set of Monte Carlo trial moves. Results from the fcc lattice proteins are directly compared with those obtained from a previous lattice protein folding study with a similar methodology on the SC lattice. A thermodynamic analysis shows comparable folding behavior between the two lattice geometries, but with a greater rate of hydrophobic-core formation persisting into lower temperatures on the fcc lattice.

Water-based binder with easy reuse characteristics for silicon/graphite anodes in lithium-ion batteries

A new binder, poly(2-propenoic acid, 2-methyl-, 3-[(2-aminoethyl) amino]-2-hydroxypropyl ester) (P-HAEAPMA), is synthesized and applied to silicon/graphite (Si/graphite) anodes in lithium-ion batteries. The Si/graphite anode with the binder exhibits good electrochemical stability. Furthermore, the materials on the discarded Si/graphite/P-HAEAPMA electrode can be recycled for use based on water because the P-HAEAPMA binder is easily soluble in water. The discharge capacity and capacity retention rate of the electrode with reused materials are slightly lower than those of the original Si/graphite/P-HAEAPMA electrode. The binder is rich in polar amino and hydroxyl groups, which not only helps to form strong adhesion between the electrode active material and copper foil but also promotes the transport of Li ions. The electrochemical performance of the electrode with the P-HAEAPMA binder is significantly enhanced compared with that of the electrode with the traditional PVDF binder or water-based LA133 binder. After 305 cycles, a specific capacity of 485.0 mA h g−1 and a capacity retention rate of 74.8% are achieved for the Si/graphite/P-HAEAPMA electrode. A binder, poly(2-propenoic acid, 2-methyl-, 3-[(2-aminoethyl) amino]-2-hydroxypropyl ester) (P-HAEAPMA), is synthesized and applied to silicon/graphite anodes in lithium-ion batteries, which exhibits good electrochemical stability. After 305 cycles, a specific capacity of 485.0 mA h g−1 and a capacity retention rate of 74.8% are achieved. Moreover, the discarded electrode with P-HAEAPMA binder can be reused just based on water because the P-HAEAPMA binder is easily soluble in water, and the electrochemical properties of the electrode with reused materials are slightly lower than those of the original electrode.

Charge effects on the behavior of CTAB adsorbed on Au(111) electrodes in aqueous solutions

The behavior of adsorbed CTAB on Au(111) electrodes has been studied using electrochemical and FTIR experiments in different aqueous solutions. The results show that the adsorbed layer is stable in acidic solutions in the whole potential range of study. The observed electrochemical and FTIR behavior is compatible with the formation of a membrane of CTA+ on the electrode surface with the polar amino groups in contact with the surface. When the electrode charge is negative, the polar groups are attracted to the surface, so that the capacitance of the electrode is smaller than that recorded for the unmodified Au(111) electrode. As the charge becomes positive, the membrane detaches from the surface and water molecules permeate through it, changing the capacitance of the electrode and giving rise to characteristic peaks in the voltammetric profile. At potentials higher than these peaks, the behavior of the electrode is comparable to that observed for the unmodified electrode. The stability of the membrane is facilitated by the incorporation of anions of the supporting electrolyte. Those anions remain on the membrane even when the electrode is transferred to a different solution, as the electrochemical behavior shows.

Design, synthesis, and biological evaluation of new raloxifene analogues of improved antagonist activity and endometrial safety

Raloxifene agonism of estrogen receptor (ER) in post-menopausal endometrium is not negligible. Based on a rational drug design workflow, we synthesized 14 analogues of raloxifene bearing a polar group in the aromatic ring of the basic side chain (BSC) and/or changes in the bulkiness of the BSC amino group. Analogues with a polar BSC aromatic ring and amino group substituents of increasing volume displayed increasing ER antagonism in Ishikawa cells. Analogues with cyclohexylaminoethoxy (13a) or adamantylaminoethoxy BSC (13b) lacking a polar aromatic ring displayed high ER-binding affinity and ER antagonism in Ishikawa cells higher than raloxifene and similar to fulvestrant (ICI182,780). The endometrial surface epithelium of immature female CD1 mice injected with 13b was comparable to that of vehicle-treated mice, while that of mice treated with estradiol, raloxifene or 13b in combination with estradiol was hyperplastic. These findings indicate that raloxifene analogues with a bulky BSC amino group could provide for higher endometrial safety treatment of the menopausal syndrome.

Development of a new bread type supplemented iron and folic acid– Chemical and technological characterization

Bread is a staple food prepared by baking a dough of flour and water. The virtually infinite combinations of different flours and differing proportions of ingredients has resulted in the wide variety of types, shapes, sizes, and textures available around the world. Considering the worldwide consume of this staple food, this study aimed to develop and assess the chemical and technological characteristics of a new biofortified blend, containing wheat, locust bean flours, iron and folic acid (applied in the form of powder or microcapsules), for the production of bread with nutritional and prophylactic characteristics for human health. Besides bread wheat properties for baking, locust wheat flours was added to the blend in a small amount (0.5%) to increase water absorbance through its polar amino groups of proteins, whereas folic acid and iron inclusion considered the human needs on a daily basis. An 85.89- and 3.93-fold increases for folic acid and iron was carried out through fortification. It was found that, relatively to wheat flour T65, the contents of some minerals (Ca, K, Si), fatty acids (C16:0, C16:1, C18:0, C18:1; C20:1) and sugars (raffinose, sucrose, glucose and fructose) were significantly higher in locust bean flour. Upon blends iron and folic acid fortification, toughness, deformation work / gluten strength and the elasticity index prevailed when powder was used, whereas minimum values were obtained for ash, toughness and gluten strength in the standard blend. Moreover, significant differences were not found for fatty acids. In bread biofortified with folic and iron in the form of powder, all fatty acids (excepting C18:2 and C18:3) prevailed, but lower values were found for sugars and total soluble solids. Moreover, breads height, weight, specific volume remained higher in standard bread, but upon application of benzoic acid or methyl 4-hydroxybenzoate lower shelf life values were found. Although from a hedonic perspective, consumers preferred the standard bread, the biofortified blend revealed a high-quality index suitable for development of a functional staple food incorporating iron and folic acid (in the form of powder or microcapsules). Nevertheless, folic acid as proved to be highly labile during baking, but incorporation of microcapsules slightly limited this degradation. Considering the shelf life of the biofortified bread, pulverization with methyl p-hydroxybenzoate seemed to be the most effective additive.

Mechanisms of the interaction of bovine serum albumin with anticancer drug gemcitabine

We investigated quantum-chemical characteristics of gemcitabine (GEM), fluorescence quenching of bovine serum albumin (BSA) in aqueous solutions with the presence of GEM. The static mechanism of the complex formation with moderate binding constant () and number of binding sites was established to take place in the solutions. Studying the energy transfer efficiency we found that molecules of GEM are localized near polar charged amino acid residues of the protein biomolecules at the average distance The calculated thermodynamic parameters demonstrate the presence of both hydrogen bonds and hydrophobic interaction between the protein and ligand molecules.

ZnO/Carbon xerogel photocatalysts by low-pressure plasma treatment, the role of the carbon substrate and its plasma functionalization

ZnO is known to be photocatalytic, but with limited performances due to the strong electron-hole recombination after irradiation. The integration of ZnO nanomaterials on a conductive and high surface area carbon substrate is thus a potential alternative to obtain a significant improvement of the photocatalytic performance. Moreover, the carbon functionalization is expected to have a significant role in the adsorption/degradation mechanisms of dye, due to the difference in wettability or surface charge.In this view, ZnO photocatalytic nanoparticles have been deposited on high surface area carbon xerogel substrate (CXG), using a new and original plasma process, consisting in the degradation of a solid organometallic directly on the carbon substrate (no gaseous precursor). In addition to the ZnO nanoparticle formation, the plasma treatment allows the carbon functionalization. The ZnO/CXG composite has been tested for the degradation of Rhodamine B (RhB) in aqueous media and compared with and O2 or NH3 plasma-treated xerogels (without nanoparticles) to identify the significant role of the substrate and its modification in the RhB adsorption and degradation mechanism.The high photocatalytic activity of ZnO/CXG composite is attributed to (i) the formation of small (8–10 nm) and well-crystallized ZnO nanoparticles anchored to the carbon substrate and (ii) to the modification of the xerogel surface chemistry. Indeed, O2 plasma treatment of the CXG promotes the generation of hydroxyl, carbonyl and carboxyl surface functional groups, which are polar and acidic, while the NH3 plasma treatment mainly leads to the formation of polar and basic amino groups. While both plasma treatments promote the formation of polar functional groups, which enhance the CXG wettability, the formation of acidic groups is identified as beneficial for the adsorption of the RhB dye, while basic groups are detrimental.

Construction of R16F and D19L mutations in the loop I of bile salt hydrolase (BSH) enzyme from Lactobacillus plantarum B14 and structural and functional analysis of the mutant BSHs

ABSTRACTBile salt hydrolase (BSH), found commonly in intestinal species of Lactobacillus and Bifidobacterium, catalyzes the hydrolysis of glycine or taurine-conjugated bile acids into the amino acids and free bile acids. Deconjugated bile acids potentially play an important role in the reduction of blood cholesterol level and formation of some gastrointestinal diseases such as cholestasis, gallstone formation, and colon cancer. Although the crystal and three-dimensional structures of BSH enzyme are known, the working mechanism of catalytic activity of such an important BSH enzyme is not known very well. Previous in silico analysis of multiple BSH has identified that Arginine-16 (R16) and Aspartate-19 (D19) were catalytically important residues in the active site of BSH. To confirm the function of these amino acids, in this study, BSH enzyme from Lactobacillus plantarum B14 strain was cloned into Escherichia coli and strictly conserved polar R16 and D19 amino acids of BSH enzyme were substituted for hydrophobic Phenylalanine-16 (F16) and Leucine-19 (L19) amino acids, respectively, by polymerase chain reaction (PCR)-based site-directed mutagenesis. The effects of the mutations on catalytic activity and structure of the BSH enzymes were detected by ninhidrin assay and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis, respectively. Research results showed that although F16 mutation led to loss of enzyme activity completely, L19 mutation led to abolishment of the synthesis of BSH enzyme. These results indicated that R16 and D19 amino acids located in loop I of the BSH enzyme might be critical for catalytic activity and assembly of the BSH enzyme respectively.