The effect of octenyl succinic anhydride-modified chitosan coating on DHA-loaded nanoemulsions: Physichemical stability and in vitro digestibility

Octenyl succinic anhydride-modified chitosan (OSA-CS) was synthesized and applied as a coating material to enhance the stability of docosahexaenoic acid (DHA)-loaded nanoemulsion. Due to the presence of the positively charged OSA-CS coating, the nanoemulsion exhibited a high positive zeta potential and two different layers. Compared with natural CS-coated nanoemulsion, OSA-CS-coated nanoemulsion showed improved storage stability (physical and chemical stability) and stability against environmental stresses (ionic strengths, temperatures and pH). Besides, OSA-CS-coated nanoemulsion protected encapsulated DHA from simulated gastric fluid damage better than that of natural CS-coated nanoemulsion, suggesting that OSA-CS-coated nanoemulsion had the potential to deliver more DHA into the small intestine. In conclusion, based on the comparison of two coating materials, natural chitosan and OSA-CS, it was found that the encapsulated nutrient was better protected by the OSA-CS coating. Such a finding will provide insights to broaden the application of modified chitosan in food delivery systems.

Release kinetic modeling of Satureja Khuzestanica Jamzad essential oil from fish gelatin/succinic anhydride starch nanocomposite films: The effects of temperature and nanocellulose concentration

Fish gelatin (FG) and octenyl succinic anhydride starch (OSAS) composite films loaded with 1, 2, 3 and 4 wt% bacterial nanocellulose (BNC) and Satureja Khuzestanica Jamzad essential oil (SKEO) were achieved successfully and their physicochemical and release properties were investigated. The results revealed that incorporation of BNC improved the tensile strength which was associated with FE-SEM, FTIR and XRD. Moreover, this study focused on the release modeling of SKEO in 4, 25 and 37 °C from nanocomposite films using different release kinetic and Arrhenius models. Also, analysis of variance-simultaneous component analysis (ASCA) and exploratory data visualization by principal component analysis (PCA) were carried out to investigate the effects of two controlled factors. Consequently, the Peleg model showed the best fitting of experimental data. The activation energies decreased by increasing the BNC concentration. This research demonstrated the nanocomposite film containing SKEO would be a suitable candidate for active food packaging.

Improved viability of probiotics by encapsulation in chickpea protein matrix during simulated gastrointestinal digestion by succinylated modification

The potential application of succinylated chickpea protein (SCP) as a wall material for spray-dried microencapsulated probiotics was investigated. The results showed that succinylation increased the surface charge of chickpea proteins (CP) and reduced the particle size of the proteins. Meanwhile, succinylated modification decreased the solubility of protein under acidic conditions and increased the solubility in alkaline conditions. The effects of spray drying and in vitro gastrointestinal digestion on probiotics were investigated by microencapsulating chickpea protein with different degrees of N-succinylation. The results showed that all microcapsules had similar morphology, particle size and low water content. The microcapsules prepared by succinylated chickpea protein showed better stability and viability during spray drying and gastrointestinal digestion. The protective effect of probiotics was better as the degree of N-succinylation increased. In particular, the SCP-3-P sample (10 % succinic anhydride modified CP and maltodextrin) lost only 0.29 Log CFU/g throughout gastrointestinal digestion. The superior protective effect provided by succinylated CP in simulated gastric fluid (SGF) was mainly attributed to the reaction of succinic anhydride with protein to cause protein aggregation under gastric acidic conditions, reducing the infiltration of gastric acid and pepsin and maintaining the structural integrity of the microcapsules. Therefore, these findings provide a new strategy for probiotic intestinal delivery and application of chickpea protein.

Addition of Canna edulis starch and starch nanoparticles to stabilized Pickering emulsions: In vitro digestion and fecal fermentation

Starch nanoparticles (SNPs) were prepared through acid hydrolysis of Canna edulis native starch and modified with octenyl succinic anhydride (OSA) to yield OS-starch and OS-SNPs. These modified particles were used to stabilize curcumin-loaded Pickering emulsions. Effects on gut microbiota during in vitro fecal fermentation were examined. The surface of OS-starch exhibits a porous structure, while OS-SNPs display layered grooves. OSA modification was confirmed by Fourier transform infrared spectroscopy (with peaks at 1728 cm-1 and 1573 cm-1) and proton nuclear magnetic resonance spectra (0.5-2 ppm). The degree of substitution for OS-starch and OS-SNPs is 0.0106 ± 0.0004 and 0.0079 ± 0.0003, respectively. Following modification, the crystallinity decreased from 35.69 ± 0.46 % (native starch) to 30.17 ± 0.70 % (OS-starch), SNPs decreased from 45.87 ± 0.89 % to 43.63 ± 0.64 % (OS-SNPs). Contact angles for OS-starch and OS-SNPs are 77.47 ± 1.78 and 55.57 ± 0.21, respectively. OS-SNPs exhibited superior emulsification properties compared to OS-starch, forming stable Pickering emulsions with pseudoplastic fluid behavior and enhanced curcumin storage protection over 14 days (60.88 ± 4.26 %) with controlled release. Stabilizing Pickering emulsions with OS-starch and OS-SNPs positively affected on gut microbiota and improved the intestinal environment, showing promise for their application in transportation systems and innovative prebiotic food formulations.

Encapsulation of ferulic acid in high internal phase Pickering emulsions stabilized using nonenyl succinic anhydride (NSA) and octenyl succinic anhydride (OSA) modified quinoa and maize starch nanoparticles

High internal phase Pickering emulsions (HIPPEs) stabilized using modified starch nanoparticles (SNPs) were studied as a delivery system for ferulic acid (FA). The quinoa (Q, 153 nm) and maize (M, 221 nm) SNPs were prepared by sono-precipitation and modified with nonenyl succinic anhydride (NSA) and octenyl succinic acid (OSA). The FA-encapsulated HIPPEs obtained showed neither coalescence nor Ostwald ripening, as reflected by emulsion index and droplet size measurements. Confocal laser scanning microscopy revealed FA entrapped droplets surrounded by the SNPs layer. The rheological measurements confirmed strong network formation and long-term stability. In vitro studies (pH 7.4, 96 h) showed sustained release of FA from the gel network. After 15 days, the encapsulation efficiencies for HIPPEs stabilized with both NSA and OSA modified QSNPs and MSNPs were close to 99%. The results showed that FA could be feasibly encapsulated in HIPPEs stabilized using modified SNPs.

Self-Assembled Amphiphilic Chitosan Nanomicelles: Synthesis, Characterization and Antibacterial Activity

Although amphiphilic chitosan has been widely studied as a drug carrier for drug delivery, fewer studies have been conducted on the antimicrobial activity of amphiphilic chitosan. In this study, we successfully synthesized deoxycholic acid-modified chitosan (CS-DA) by grafting deoxycholic acid (DA) onto chitosan C2-NH2, followed by grafting succinic anhydride, to prepare a novel amphiphilic chitosan (CS-DA-SA). The substitution degree was 23.93% for deoxycholic acid and 29.25% for succinic anhydride. Both CS-DA and CS-DA-SA showed good blood compatibility. Notably, the synthesized CS-DA-SA can self-assemble to form nanomicelles at low concentrations in an aqueous environment. The results of CS, CS-DA, and CS-DA-SA against Escherichia coli and Staphylococcus aureus showed that CS-DA and CS-DA-SA exhibited stronger antimicrobial effects than CS. CS-DA-SA may exert its antimicrobial effect by disrupting cell membranes or forming a membrane on the cell surface. Overall, the novel CS-DA-SA biomaterials have a promising future in antibacterial therapy.

Novel Carboxylation Method for Polyetheretherketone (PEEK) Surface Modification Using Friedel-Crafts Acylation

Recently, polyetheretherketone (PEEK) has shown promising dental applications. Surface treatment is essential for dental applications owing to its poor surface energy and wettability; however, no consensus on an effective treatment method has been achieved. In this study, we attempted to carboxylate PEEK sample surfaces via Friedel-Crafts acylation using succinic anhydride and AlBr3. The possibility of further chemical modifications using carboxyl groups was examined. The samples were subjected to dehydration-condensation reactions with 1H,1H-pentadecafluorooctylamine and N,N'-dicyclohexylcarbodiimide. Furthermore, the sample's surface properties at each reaction stage were evaluated. An absorption band in the 3300-3500 cm-1 wavenumber region was observed. Additionally, peak suggestive of COOH was observed in the sample spectra. Secondary modification diminished the absorption band in 3300-3500 cm-1 and a clear F1s signal was observed. Thus, Friedel-Crafts acylation with succinic anhydride produced carboxyl groups on the PEEK sample surfaces. Further chemical modification of the carboxyl groups by dehydration-condensation reactions is also possible. Thus, a series of reactions can be employed to impart desired chemical structures to PEEK surfaces.

Product study of the reactions of γ-caprolactone and γ-heptalactone initiated by OH radicals at 298 K and atmospheric pressure: Formation of acyl peroxynitrates (APN)

A product study was performed for the reaction of γ-caprolactone (GCL) and γ-heptalactone (GHL) initiated by OH radicals at (298 ± 2) K and atmospheric pressure, in presence of NO_x. The identification and quantification of the products were performed in a glass reactor coupled with in situ FT-IR spectroscopy. The following products were identified and quantified with the corresponding formation yields (in %) for the OH + GCL reaction: peroxy propionyl nitrate (PPN) (52 ± 3), peroxy acetyl nitrate (PAN) (25 ± 1), and succinic anhydride (48 ± 2). For the GHL + OH reaction, the products detected with their corresponding formation yields (in %) were the following: peroxy n-butyryl nitrate (PnBN) (56 ± 2), peroxy propionyl nitrate (PPN) (30 ± 1) and succinic anhydride and (35 ± 1). Upon these results, an oxidation mechanism is postulated for the title reactions. The positions with the highest H-abstraction probabilities for both lactones are analyzed. Specifically, the increased reactivity of the C5 site, as indicated by structure reactivity estimations (SAR), is suggested by the identified products. For both GCL and GHL degradation appears to follow degradation paths including ring preservation and opening. The atmospheric implications of the APN formation as a photochemical pollutant and as NO_x reservoirs of species is assessed.

Synthesis, characterization and adsorption behavior of modified cellulose nanocrystals towards different cationic dyes

Green and efficient removal of polluted materials are essential for the sustainability of a clean and green environment. Nanomaterials, particularly cellulose nanocrystals (CNCs), are abundant in nature and can be extracted from various sources, including cotton, rice, wheat, and plants. CNCs are renewable biomass materials with a high concentration of polar functional groups. This study used succinic anhydride to modify the surface of native cellulose nanocrystals (NCNCs). Succinic anhydride has been frequently used in adhesives and sealant chemicals for a long time, and here, it is evaluated for dye removal performance. The morphology and modification of CNCs studied using FTIR, TGA & DTG, XRD, SEM, AFM, and TEM. The ability of modified cellulose nanocrystals (MCNCs) to adsorb cationic golden yellow dye and methylene blue dye was investigated. The MCNCs exhibited high adsorption affinity for the two different cationic dyes. The maximum adsorption efficiency of NCNCs and MCNCs towards the cationic dye was 0.009 and 0.156 wt%. The investigation for adhesive properties is based on the strength and toughness of MCNCs. MCNCs demonstrated improved tensile strength (2350 MPa) and modulus (13.9 MPa) using E-51 epoxy system and a curing agent compared to 3 wt% composites. This research lays the groundwork for environmentally friendly fabrication and consumption in the industrial sector.

Production and Anti-Inflammatory Performance of PVA Hydrogels Loaded with Curcumin Encapsulated in Octenyl Succinic Anhydride Modified Schizophyllan as Wound Dressings

Amphiphilic polysaccharides can be used as wall materials and applied to encapsulate hydrophobic active chemicals; moreover, there is significant demand for novel medical high-molecular-weight materials with various functions. In order to prepare amphiphilic schizophyllan (SPG), octenyl succinic anhydride (OSA) was chosen to synthesize OSA-modified schizophyllan (OSSPG) using an esterified reaction. The modification of OSSPG was demonstrated through FT-IR and thermal analysis. Moreover, it was found that OSSPG has a better capacity for loading curcumin, and the loading amount was 20 μg/mg, which was 2.6 times higher than that of SPG. In addition, a hydrogel made up of PVA, borax, and C-OSSPG (OSSPG loaded with curcumin) was prepared by means of the one-pot method, based on the biological effects of curcumin and the immune-activating properties of SPG. The mechanical properties and biological activity of the hydrogel were investigated. The experimental results show that the dynamic cross-linking of PVA and borax provided the C-OSSPG/BP hydrogel dressing with exceptional self-healing properties, and it was discovered that the C-OSSPG content increased the hydrogel's swelling and moisturizing properties. In fibroblast cell tests, the cells treated with hydrogel had survival rates of 80% or above. Furthermore, a hydrogel containing C-OSSPG could effectively promote cell migration. Due to the excellent anti-inflammatory properties of curcumin, the hydrogel also significantly reduces the generation of inflammatory factors, such as TNF-α and IL-6, and thus has a potential application as a wound dressing medicinal material.

Comparative characterization of sugar beet fibers to sugar beet pectin and octenyl succinic anhydride modified maltodextrin in aqueous solutions using viscometry, conductometry, tensiometry and component analysis

BACKGROUND

Knowledge about specific functional characteristics, such as viscosimetric, conductometric, tensiometric and structural properties of polysaccharide aqueous solutions is highly important in the successful and adequate application in food emulsion formulation. For the first time detailed characterization of sugar beet fibers aqueous solutions in comparison to high molecular weight (sugar beet pectin) and low molecular weight [octenyl succinic anhydride (OSA) maltodextrin] hydrocolloids/stabilizers was performed through viscometry, conductometry, tensiometry and component analysis.

RESULTS

Sugar beet fibers and its water-soluble fraction were investigated. All sugar beet fiber samples showed substantial surface-active properties but different effect on the viscosity values of aqueous solutions. Sugar beet pectin had higher impact on aqueous solutions viscosity values compared to sugar beet fiber samples. Structural bonding between investigated polysaccharides were evaluated through conductometric measurements. Intermolecular linking and probable embedding of OSA maltodextrin molecules into the sugar beet fiber complex structure was detected in conductometric studies. The increased concentration of sugar beet fibers in the presence of sugar beet pectin led to the accelerated increase in specific conductivity values indicating effects of 'macromolecular crowding', intermolecular and intramolecular conformation changes and charge formation.

CONCLUSIONS

Detailed characterization of sugar beet fibers provided scientific insight towards fundamental characteristics of sugar beet fiber aqueous solutions. The presented characteristics are particularly applicable in the field of food emulsion stabilization due to the presented surface-active properties of sugar beet fibers as well as specific characteristics of investigated multi-polysaccharide systems. © 2022 Society of Chemical Industry.

Relationship between flexibility and interfacial functional properties of soy protein isolate: succinylation modification

BACKGROUND

In this paper, the effects of different succinic anhydride (SA) additions on the flexibility of soy protein isolate (SPI) were investigated, and changes in protein conformation and interfacial functional properties were measured. The structure-effect relationship between conformation, flexibility, and interfacial functional properties was established.

RESULTS

SPI was bound to SA through disulfide bonds, and the zeta potential was reduced. The β-sheet content decreased, the disordered structure increased, and there were changes in tertiary structure and microstructure. The surface hydrophobicity, disulfide bond content, and solution turbidity were reduced to 5063, 1.0967 μmol g-1 , and 0.0036 μmol g-1 respectively. The best flexibility of SPI (0.3977) and interfacial functional properties were obtained when the mass ratio of SA/SPI was 15%. Correlation analysis showed a highly significant positive correlation (P < 0.01) between flexibility and emulsification and foaming properties, with correlation coefficients of 0.960 and 0.942 for flexibility with emulsifying activity and emulsion stability respectively, and 0.972 and 0.929 for flexibility with foaming capacity and foaming stability respectively.

CONCLUSION

The results suggest that succinylation-induced conformational changes of SPI improved its interfacial functional properties by changing its flexibility. These results provide theoretical guidelines for the development and application of highly emulsifiable and stable soy protein products utilizing succinylation. © 2022 Society of Chemical Industry.

Stable O/W emulsions and oleogels with amphiphilic konjac glucomannan network: preparation, characterization, and application

BACKGROUND

The stabilization of oil-in-water (O/W) emulsions has long been explored. Assembly of polymer networks is an effective method for stabilizing O/W emulsions. Konjac glucomannan (KGM) is a plant polysaccharide and the network of KGM gel is a good candidate for stabilizing O/W emulsions based on its high viscosity and thickening properties. However, natural KGM has strong hydrophilicity and is not able to offer interfacial activity. Octenyl succinic anhydride (OSA) is a hydrophobic molecule, which is widely used as thickener and stabilizer in food emulsions. In this work, the amphiphilic biopolymer (OSA-KGM) was fabricated by modifying the KGM with OSA. Furthermore, OSA-KGM biopolymer was used to prepare O/W emulsions, which were then freeze-dried and used to prepare oleogels as fat substitute for bakery products.

RESULTS

OSA-KGM had advanced hydrophobicity with water contact angle 81.13° and adsorption behavior at the oil-water interface, with interfacial tension decreasing from 18.52 to 13.57 mN m^-1 within 1 h. The emulsification of OSA-KGM remarkably improved the stability of emulsions without phase separation during storage for 31 days. Oleogels with OSA-KGM showed good thixotropic and structure recovery properties (approximately 100%) and low oil loss (from 69.5% to 50.4%). Cakes made from oleogels had a softer texture than cakes made from peanut oil and margarine.

CONCLUSION

Amphiphilic biopolymer OSA-KGM shows advanced interfacial activity and hydrophobicity. This paper provides an insight into preparing stable O/W emulsions with a new biopolymer and oleogels potentially applied as fat substitute in bakery products. © 2022 Society of Chemical Industry.

Application of Curcumin Emulsion Carrier from Ultrasonic-Assisted Prepared Octenyl Succinic Anhydride Rice Starch

The emulsification of ultrasonic-assisted prepared octenyl succinic anhydride (OSA) rice starch on curcumin was investigated in the present study. The results indicated that the encapsulation efficiency of curcumin in emulsions stabilized by OSA-ultrasonic treatment rice starch was improved, from 81.65 ± 0.14% to 89.03 ± 0.09%. During the in vitro oral digestion, the particle size and Zeta potential of the curcumin emulsion did not change significantly (p > 0.05). During the in vitro digestive stage of the stomach and small intestine, the particle size of the curcumin emulsion continued to increase, and the absolute potential continued to decrease. Our work showed that OSA-pre-treatment ultrasonic rice starch could improve curcumin bioavailability by increasing the encapsulation efficiency with stronger stability to avoid the attack of enzymes and high intensity ion, providing a way to develop new emulsion-based delivery systems for bioactive lipophilic compounds using OSA starch.

Revealing substitution priority and pattern of octenylsuccinic groups along the starch chain under a continuous mode

Octenylsuccinic (OS) groups distribution was considered random under traditional batch mode (BM) process due to excessive available octenyl succinic anhydride (OSA) at early stage, making the functionality optimization of OSA starch under restricted substitution degree (DS) difficult. To reveal the priority rule of substituent position at starch molecular level, a continuous mode (CM, dropwise OSA addition) was applied for OSA starch preparation. Initial OSA substitution was predominately at the branching points of amylopectin backbone, then successive at the branching points of shorter and longer chains with increasing DS. As DS increased over 1.49%, substitution started occurring along the chains and moved towards the non-reducing ends until DS reached 6.65%. At similar DS, more branching point substitutions occurred at CM starch, showing superior emulsifying property over BM starch. OSA substitution priority rule does exist under controlled OSA supply, which would facilitate OSA starch design with specific substitution pattern and favored functionality.

Octenyl Succinate Modification of Starch Enhances the Formation of Starch-Lipid Complexes

The present study investigated the effect of octenyl succinic anhydride (OSA) modification of starch on the formation of starch-lipid complexes. The complexing index (CI) showed that native maize starch (NMS) formed more complexes with monopalmityl glycerol (MPG) than with palmitic acid (PA), whereas dipalmityl glycerol (DPG) was not effective in forming complexes with NMS. After OSA modification, the complexation between OSA-starch and lipids was greatly enhanced, especially for PA and DPG, and the CI values increased from 79.6 to 93.3% for OSA-starch-PA and from 80.3 to 93.2% for OSA-starch-DPG complexes with increasing DS of OSA-starch. Structural analyses showed that OSA-starch-lipid complexes had higher degrees of long- and short-range molecular orders than the corresponding NMS-lipid complexes. This study showed for the first time that DPG can form complexes with OSA-starch, which was attributed to the increased dispersion of DPG in water by the emulsifying ability of OSA-starch. The finding is of great significance for a better understanding of the formation of starch-lipid complexes.

Quinoa starch granules: a candidate for stabilising food-grade Pickering emulsions

BACKGROUND

Particle-stabilised emulsions, so-called Pickering emulsions, are known to possess many beneficial properties, including being extremely stable. Starch granules isolated from quinoa have been used as emulsion stabilising particles. The granules were intact, 1-3 µm in diameter and modified with octenyl succinic anhydride to increase their hydrophobicity. Starch granules, as opposed to most other particles used to generate Pickering emulsions, are edible, abundant and derived from natural sources.

RESULTS

Emulsions produced by high shear homogenisation had droplet sizes of 9-70 µm depending on the starch-to-oil ratio. Droplet size decreased with increasing starch-to-oil ratio, but was unaffected by the oil phase volume over a range of 5-33% oil (v/v). Although the drops were large and subject to creaming, their size remained unchanged over a period of 7 days. By adjusting the starch-to-oil ratio drops could be made to be buoyancy neutral to prevent creaming. Rheological characterisation indicated a gel structure with an elastic modulus in the range 200-2000 Pa depending on droplet size.

CONCLUSION

This work has demonstrated the successful use of starch granules to stabilise emulsions which may find applications beyond that of food, for example in cosmetics and pharmaceutical formulations.

Facile one-pot preparation, surface functionalization, and toxicity assay of APTS-coated iron oxide nanoparticles

We report a facile approach to synthesizing 3-aminopropyltrimethoxysilane (APTS)-coated magnetic iron oxide (Fe(3)O(4)@APTS) nanoparticles (NPs) with tunable surface functional groups for potential biomedical applications. The Fe(3)O(4) NPs with a mean diameter of 6.5 nm were synthesized by a hydrothermal route in the presence of APTS. The formed amine-surfaced Fe(3)O(4)@APTS NPs were further chemically modified with acetic anhydride and succinic anhydride to generate neutral (Fe(3)O(4)@APTS⋅Ac) and negatively charged (Fe(3)O(4)@APTS⋅SAH) NPs. These differently functionalized NPs were extensively characterized by x-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetry analysis, zeta potential measurements, and T(2) relaxometry. The cytotoxicity of the particles was evaluated by in vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric viability assay of cells along with microscopic observation of cell morphology. The hemocompatibility of the particles was assessed by in vitro hemolysis assay. We show that the hydrothermal approach enables an efficient modification of APTS onto the Fe(3)O(4) NP surfaces and the formed NPs with different surface charge polarities are water-dispersible and colloidally stable. The acetylated Fe(3)O(4)@APTS⋅Ac NPs displayed good biocompatibility and hemocompatibility in the concentration range of 0-100 µg ml(-1), while the pristine Fe(3)O(4)@APTS and Fe(3)O(4)@APTS⋅SAH particles started to display slight cytotoxicity at a concentration of 10 µg ml(-1). The findings from this study suggest that the Fe(3)O(4)@APTS NPs synthesized by the one-pot hydrothermal route can be surface modified for various potential biomedical applications.

A rapid approach for isobaric peptide termini labeling

Isobaric peptide termini labeling (IPTL) is a recently introduced approach to the chemical labeling of peptides with isotopic reagents. Peptides derived from two different samples are labeled at the N terminus and at the C terminus with isotopically labeled reagents that have identical mass differences. To obtain isobaric peptides, labeling is carried out such that the introduced mass increase at one terminus will exactly match the mass decrease at the other terminus (and the other way around). This results in product ion spectra that display the quantitative difference of the peptide signal derived from the two samples for every b-ion and y-ion in the spectrum. The original IPTL approach required the selective modification of lysines followed by C-18 micropurification of modified peptides and reaction of the N termini. Here, we describe a new approach for IPTL that is based on the selective modification of the peptide N termini with succinic anhydride and subsequent reductive amination of C-terminal lysines with formaldehyde and cyanoborohydride. Both reactions can be carried out in one pot within 10 min and without C-18 micropurification. In addition, we present the software package IsobariQ for straightforward data analysis.

Adsorption of Cu(II), Cd(II), and Pb(II) from aqueous single metal solutions by cellulose and mercerized cellulose chemically modified with succinic anhydride

This work describes the preparation of new chelating material from mercerized cellulose. The first part treats the chemical modification of non-mercerized cellulose (cell 1) and mercerized cellulose (cell 2) with succinic anhydride. Mass percent gains (mpg) and degree of succinylation (DS) of cell 3 (from cell 1) and cell 4 (from cell 2) were calculated. Cell 4 in relation to cell 3 exhibited an increase in mpg and in the concentration of carboxylic functions of 68.9% and 2.8 mmol/g, respectively. Cells 5 and 6 were obtained by treatment of cells 3 and 4 with bicarbonate solution to release the carboxylate functions and characterized by FTIR. The second part compares the adsorption capacity of cells 5 and 6 for Cu2+, Cd2+, and Pb2+ ions in an aqueous single metal solution. Adsorption isotherms were developed using Langmuir model. Cell 6 in relation to cell 5 exhibited an increase in Qmax for Cu2+ (30.4 mg/g), Cd2+ (86.0 mg/g) and Pb2+ (205.9 mg/g).

Body Distributioin of RGD-mediated Liposome in Brain-targeting Drug Delivery

RGD conjugation liposomes (RGD-liposomes) were evaluated for brain-targeting drug delivery. The flow cytometric in vitro study demonstrated that RGD-liposomes could bind to monocytes and neutrophils effectively. Ferulic acid (4-hydroxy-3-methoxycinnamic, FA) was loaded into liposomes. Rats were subjected to intrastriatal microinjections of 100 units of human recombinant IL-1beta to produce brain inflammation and caudal vein injection of three formulations (FA solution, FA liposome and RGD-coated FA liposome). Animals were sacrificed 15, 30, 60 and 120 min after administration to study the body distribution of the FA in the three formulations. HPLC was used to determine the concentration of FA in vivo with salicylic acid as internal standard. The results of body distribution indicated that RGD-coated liposomes could be mediated into the brain with a 6-fold FA concentration compared to FA solution and 3-fold in comparison to uncoated liposome. Brain targeted delivery was achieved and a reduction in dosage might be allowed.

Solid-phase extraction of N-linked glycopeptides

Protein glycosylation is a common post-translational modification and has been increasingly recognized as one of the most prominent biochemical alterations associated with malignant transformation and tumorigenesis. N-linked glycosylation is prevalent in proteins on the extracellular membrane, and many clinical biomarkers and therapeutic targets are glycoproteins. Here, we describe a protocol for solid-phase extraction of N-linked glycopeptides and subsequent identification of N-linked glycosylation sites (N-glycosites) by tandem mass spectrometry. The method oxidizes the carbohydrates in glycopeptides into aldehydes, which can be immobilized on a solid support. The N-linked glycopeptides are then optionally labeled with a stable isotope using deuterium-labeled succinic anhydride and the peptide moieties are released by peptide-N-glycosidase. In a single analysis, the method identifies hundreds of N-linked glycoproteins, the site(s) of N-linked glycosylation and the relative quantity of the identified glycopeptides.

Preparation of N-Succinyl-chitosan and Their Physical-Chemical Properties as a Novel Excipient

The aim of this work is to prepare N-succinyl-chitosan (Suc-Chi) and measure physical-chemical properties for Suc-Chi as excipients. Suc-Chi were prepared via ring-opening reactions with succinic anhydride in Dimethyl Sulfoxide system. The physical-chemical properties of Suc-Chi, such as the degree of substitution (DS), solubility, isoelectric point (pI), glass transition temperature (Tg), partition coefficient (P(app)) and zata potential were detected respectively in order to evaluate their possibility as drug carriers. We obtained Suc-Chi DAC-90 (DS=0.33) and the data of physical-chemical properties for the product. The knowledges of physical-chemical properties for Suc-Chi are valuable for basic or applied purposes in biomedical and pharmaceutical sciences stabilization.

Quantitative peptidomics of mouse pituitary: comparison of different stable isotopic tags

Determining the relative levels of neuropeptides in two samples is important for many biological studies. An efficient, sensitive and accurate technique for relative quantitative analysis involves tagging the peptides in the two samples with isotopically distinct labels, pooling the samples and analyzing them using liquid chromatography/mass spectrometry (LC/MS). In this study, we compared two different sets of isotopic tags for analysis of endogenous mouse pituitary peptides: succinic anhydride with either four hydrogens or deuteriums and [3-(2,5-dioxopyrrolidin-1-yloxycarbonyl)propyl]trimethylammonium chloride with either nine hydrogens or deuteriums. These two labels react with amines and impart either a negative charge (succinyl) or a positive charge (4-trimethylammoniumbutyryl (TMAB)). Every endogenous mouse pituitary peptide labeled with the light TMAB reagent eluted from the C18 reversed-phase column at essentially the same time as the corresponding peptide labeled with the heavy reagent. Most of the peptides labeled with succinyl groups also showed co-elution of the heavy- and light-labeled forms on LC/MS. The mass difference between the heavy and light TMAB reagents (9 Da per label) was larger than that of the heavy and light succinyl labels (4 Da per label), and for some peptides the larger mass difference provided more accurate determination of the relative abundance of each form. Altogether, using both labels, 82 peptides were detected in Cpe(fat/fat) mouse pituitary extracts. Of these, only 16 were detected with both labels, 41 were detected only with the TMAB label and 25 were detected only with the succinyl label. A number of these peptides were de novo sequenced using low-energy collisional tandem mass spectrometry. Whereas the succinyl group was stable to the collision-induced dissociation of the peptide, the TMAB-labeled peptides lost 59 Da per H9 TMAB group. Several peptides identified in this analysis represent previously undescribed post-translational processing products of known pituitary prohormones. In conclusion, both succinyl and TMAB isotopic labels are useful for quantitative peptidomics, and together these two labels provide more complete coverage of the endogenous peptides.

Evaluating immobilized metal affinity chromatography for the selection of histidine-containing peptides in comparative proteomics

Agarose based immobilized metal affinity chromatography (IMAC) columns loaded with copper (II) were evaluated for the selection of histidine-containing peptides in comparative proteomics. Recovery, binding specificity, and reproducibility were investigated with model proteins. Cu(II)-IMAC was found to be highly selective for histidine containing peptides; moreover, a low degree of nonspecific selection was observed. Acylation of the amino-terminus of peptides with either succinic anhydride, N-acetoxysuccinamide, or [3-(2,5)-dioxopyrrolidin-1-yloxycarbonyl)-propyl]-trimethylammonium (quaternary amine) reduced the number of histidine-containing peptides bound by the Cu(II)-IMAC columns. This provides an additional possibility for sample simplification in proteomic applications. The number of acylated peptides selected decreased in the order of quaternary amine > N-acetoxysuccinamide > succinic anhydride derivatization. Although the selection of N-terminally derivatized peptides is biased toward peptides that contain more than one histidine, it is not yet possible to predict selectivity.

[Preparation of liposomes surface-modified with glycyrrhetinic acid targeting to hepatocytes]

OBJECTIVE

To study the preparation of liposomes surface-modified with glycyrrhetinic acid targeting to hepatocytes.

METHOD

3-succinic-30-stearyl glycyrrhetinic acid(Suc-GAOSt), one of the amphiphilic glycyrrhetinic acid derivatives, was synthesized as targeting molecules, liposomes surface-modified with glycyrrhetinic acid has been produced with ethanol injection method.

RESULT

Targeting molecules can be mixed into the liposomal membrane. It was confirmed that the targeting molecules is 9% of the total lipids at the most in the liposomes.

CONCLUSION

Liposomes surface-modified with glycyrrhetinic acid was successfully prepared, which is considered to be a potential approach targeting to hepatocytes.

Chemically modified papain for applications in detergent formulations

Papain was modified using succinic anhydride, and the modified papain so obtained was compared with the native papain for its activity and stability in detergents. This study was done using commercial enzyme detergents as references. It was found that modified papain retained activity comparable to the commercial enzyme detergents. Chemically modified papain may prove to be an inexpensive alternative to alkaline proteases that are used in detergents.

Facile synthesis of optically active gamma-lactones via lipase-catalyzed reaction of 4-substituted 4-hydroxybutyramides

Lipase-catalyzed transesterification of racemic 4-substituted 4-hydroxybutyramides with succinic anhydride proceeded enantioselectively to afford (S)-succinic acid monoester and unreacted (R)-4-hydroxybutyramide derivative, which were separated easily by treatment with an alkaline solution. Both enantiomers were converted easily to optically active gamma-substituted gamma-butyrolactones.

Chemical modification of the hemolytic lectin CEL-III by succinic anhydride: involvement of amino groups in the oligomerization process

CEL-III is a Ca(2+)-dependent lectin from a marine invertebrate, Cucumaria echinata, which shows strong hemolytic activity toward human and rabbit erythrocytes. After binding to carbohydrate receptors, CEL-III oligomerizes in the erythrocyte membrane to form ion-permeable pores, leading to the colloid osmotic rupture of the cells. Since hemolysis was greatly increased in the alkaline pH, especially above pH 9, involvement of amino groups of CEL-III in its hemolytic activity was evaluated using chemical modification by succinic anhydride. After modification of 7 amino groups per protein molecule, the hemolytic activity of CEL-III was reduced to 23% of the native protein, but hemagglutinating and carbohydrate-binding activities were only slightly affected even after modification of 14 amino groups. A circular dichroism spectrum of modified CEL-III showed almost no change in the secondary structure from that of the native protein, indicating that the decrease of hemolytic activity was not caused by partial unfolding of the protein. Immunoblotting analysis of the erythrocyte membrane treated with modified CEL-III showed a decrease in the formation of CEL-III oligomer in the membrane in parallel with the decrease in hemolytic activity. These results suggest that amino groups of CEL-III are involved in its oligomerization in the cell membrane, and their modification leads to inactivation of the protein without much influence on the carbohydrate-binding activity.

In vivo evaluation of magnetite nanoparticles for use as a tumor contrast agent in MRI

Magnetite nanoparticles, coated by three different artificial polypeptides, were conjugated to an antibody specific to the carcinoembryonic antigen (CEA). To protect the particles from fast blood elimination, the coats were modified by various sugars, polyethyleneglycol, albumin, and sialoproteins, respectively. The protective effect was determined by using a specific in vitro test and by analyzing the biodistribution of the nanoparticles in nude mice grafted with CEA-tumors. In particular, a prolongation of the blood circulation time has been expected, if a natural modifier is attached to the coated nanoparticles. Although the elimination rate could hardly be decreased by any modifiers, the tumor accumulation is slightly improved by using the specific sialoprotein glycophorin B. The usefulness of nanoparticles as image contrast agents is probably limited by their microdistribution within the tumor tissue. The requirements for a contrast agent to be highly tissue specific are discussed.

Effectiveness of a new non-thrombogenic bio-adhesive in microvascular anastomoses

Negatively-charged fibrin glue was successfully prepared by combining human cryoprecipitate with succinic anhydride. The resulting bio-adhesive was tested for thrombogenicity and tensile strength by applying it to three groups of Sprague-Dawley rat femoral-artery anastomoses (6 suture, 2 suture, and no suture anastomoses). Anastomoses were tested by a standard patency test over 7 days. Both the 6-suture and 2-suture anastomoses with negatively-charged fibrin glue had 100 percent patency rates and no pseudoaneurysm formation over 7 days. When positively-charged fibrin glue was applied to sutured anastomoses, patency rates decreased gradually to 50 percent over 7 days. Fibrin glue alone (whether negatively- or positively-charged) does not have the tensile strength to maintain an anastomosis without sutures. However when applied to a two-suture anastomosis, the breaking strength of the anastomosis is more enhanced by the negatively-charged fibrin glue.

Regeneration of active receptor recognition domains on the B subunit of cholera toxin by formation of hybrids from chemically inactivated derivatives

In order to test the hypothesis that binding sites of cholera toxin for its receptor, the monosialoganglioside GM1, are shared between adjacent beta-polypeptide chains, two inactive chemical derivatives of the B subunit of cholera toxin (CTB) were prepared and were subsequently used for the construction of hybrid CTB pentamers. One inactive derivative consisted of CTB specifically modified in the single essential Trp-88 residue of each beta-chain. This residue was modified by formylation, a treatment preserving the structural integrity of CTB. The other inactive derivative consisted of CTB specifically succinylated in three amino groups located in or near the receptor binding site. Using [1,4-14C]succinic anhydride for the site-specific succinylation and analysis of radiolabeled tryptic fragments of S-carboxymethylated [14C]sssCTB revealed that the amino groups specifically modified were the alpha-amino group of Thr-1 and the epsilon-amino groups of respectively Lys-34 and Lys-91. Upon submitting equal amounts of formylated CTB and site-specific succinylated CTB to a denaturation-renaturation cycle, hybrid pentamers were formed which in contrast to the parental compounds were able to bind GM1. The affinity of hybrid CTB for GM1, as estimated by a competitive solid-phase radiobinding assay was unexpectedly high and only 2.5-fold lower than that of its native counterpart. The number of active binding sites on hybrid CTB was determined from: (i) titration with the oligosaccharide moiety of GM1 (oligo-GM1) and monitoring the reversal of the Trp fluorescence quenching by iodide ions and (ii) rapid gel filtration over a superdex HR column of a mixture of hybrid CTB and an excess of 3H-labeled oligo-GM1. The data are in agreement with the formation of one active binding per four reconstituted binding sites in hybrid CTB, which is consistent with a random association of CTB monomers during the denaturation-renaturation cycle.

Modulation of allosteric interactions in neurophysin induced by succinylation of serine-56 or cleavage of residues 1-8

Neurophysin is an allosteric protein in which peptide binding and self-association are positively linked. Reaction of neurophysin with succinic anhydride led to a large decrease in peptide affinity assignable to succinylation of a serine or threonine hydroxyl group. To identify the residue involved, acetimidated protein was reacted with [14C]succinic anhydride and the active and inactive components were separated by affinity chromatography. Performic acid oxidation and tryptic and Asp-N mapping of the two components, followed by automated Edman degradation, allowed identification of the critical residue as Ser-56. This residue is not a direct participant in peptide binding and is distant from the subunit interface of the dimer, but it is immediately adjacent to the site of one of the known mutations associated with familial diabetes insipidus. Examination in solution of the peptide affinity of neurophysin succinylated at Ser-56 indicated a binding affinity approximately 1/20th that of the native protein or of protein succinylated at other residues, and a loss of the normal dependence of binding affinity on protein concentration. Under the same buffer conditions, loss of the concentration dependence of binding, in addition to the previously demonstrated loss of binding affinity, also accompanied excision of residues 1-8, an effect attributed to the loss of binding site residue Arg-8. However, in contrast to the effects of succinylation on native neurophysin, only minor effects of succinylation on the binding affinity of the des-1-8 protein were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Breakdown of N-terminally modified peptides and an isopeptide by rumen microorganisms

Treatment of Trypticase peptides with acetic anhydride, succinic anhydride, or maleic anhydride inhibited their breakdown to ammonia by rumen microorganisms by an average of 89% after 12 h of incubation in vitro. All three treatments gave similar protection. Acetylation also protected dipeptides containing lysine and methionine from degradation. However, more effective protection was obtained by linking lysine and methionine as N-epsilon-methionyl lysine.

Effect of succinylation of oil palm protein concentrates on the functional properties

Defatted kernel flour of oil palm, grounded to 60 mesh, was taken as raw material to produce protein concentrates (70.8%) protein) which were succinylated at different levels (0.05; 0.2 and 0.6). The extent of acylation was measured as percentage of lysine modification reaching values from 18.4% to 48.6%. Protein concentrate functional properties were determined: Water solubility (pH 2-10); water absorption (320%); oil absorption (2.2 ml oil/g), emulsion activity and emulsion stability (28-46%). The functional properties were enhanced by succinylation if compared with the untreated protein concentrate, however, "in vitro" digestibility was not affected, by succinylation. In summary, the results of this study indicate that acylation using succinyl anhydride can improve the functional properties of oil palm protein concentrate over those without such treatment.

Succinylation of histone amino groups facilitates transcription of nucleosomal cores

Treatment of nucleosomal cores with succinic anhydride, which modifies preferentially the amino-terminal domains of core histones, takes place without dissociation of the particles. Low levels of modification, which cause small structural effects, are accompanied by substantial increases in the efficiency of the nucleosomal cores as in vitro transcription templates for RNA polymerase II. The transcriptional properties of the succinylated nucleosomal cores are similar to those of the acetylated particles (Piñeiro et al., (1991) Biochem. Biophys. Res. Commun. 177, 370-376), indicating that no specific blocking by acetyl residues is required to facilitate in vitro transcription. Moreover, to obtain a certain level of stimulation, a smaller number of groups has to be modified by succinic than by acetic anhydride.

Shear bond strength to dentin and Ni-Cr-Be alloy with the All-Bond universal adhesive system

The shear bond strength of the All-Bond system to dentin and a nonprecious alloy was evaluated. Eighty human molar teeth (10 per group) were used in the dentin bonding phase of the study. A bond site was prepared in dentin, and both the succinic anhydride modified HEMA and 10 percent phosphoric acid dentin conditioning techniques were evaluated under both wet and dry conditions. Eighty Rexillium III specimens were used in the metal bonding phase of the study. All-Bond primer and opaquer were applied to the metal surface, followed by a visible light-cured composite restorative material. Dentin bond strengths were determined at 24 hours, while metal bond strengths were evaluated both at 24 hours and after thermocycling (2,500 cycles). Separate groups were established for adhesion to both dentin and metal with the composite placed in a plastic matrix or a gelatin capsule. The highest mean shear bond values to dentin were obtained in the groups with the gelatin capsule bonding procedure, where the dentin was treated with 10 percent phosphoric acid and then blotted dry (wet technique) before the bonding procedure (39.99 MPa). These values were higher than the succinic anhydride modified HEMA-treated group with gentle air drying (wet technique-29.56 MPa). There was essentially no difference in mean shear bond strengths to dentin when a succinic anhydride modified HEMA dentin conditioner was used with aggressive (dry technique) or gentle air drying (wet technique) [29.56 versus 29.08 MPa]. High bond strengths to Rexillium III were obtained when the All-Bond adhesive system was used in combination with a dual-care opaquer and a composite restorative material.(ABSTRACT TRUNCATED AT 250 WORDS)

The octameric structure of beta-glucosidase from Botryodiplodia theobromae Pat

1. Whereas only beta-glucosidase A (beta-D-glucoside glucohydrolase, EC 3.2.1.21) was produced by the tropical fungus Botryodiplodia theobromae Pat. (I.M.I. 115626; A.T.C.C. 26123) in young cultures containing D-cellobiose as carbon source, lower-Mr forms (B, C and D) were found in older cultures when the pH had drifted from the initial value of pH 6.2 to pH 7.9. 2. The Michaelis constants (Km) of the various molecular forms of the enzyme were 0.30 +/- 0.03 mM-, 0.26 +/- 0.01 mM-, 0.20 +/- 0.02 mM- and 0.16 +/- 0.01 mM-o-nitrophenyl beta-D-glucopyranoside for beta-glucosidase forms A (Mr 320,000), B (Mr 160,000), C (Mr 80,000) and D (Mr 40,000) respectively. 3. Only beta-glucosidase D showed substrate inhibition. 4. Only L-arginine was found as the N-terminal residue, and beta-glucosidase A contained 31.7 +/- 0.6 mol of N-terminal L-arginine/mol of the enzyme. 5. Storage of purified beta-glucosidase A under mildly alkaline conditions caused its dissociation into the lower-Mr forms, whereas adjustment of the pH of a solution of beta-glucosidase A to pH 12.0 with 1 M-NaOH led to complete inactivation on incubation at 40 degrees C for 1 h and to the release of 25.2 +/- 1.5 mol of inorganic phosphate/mol of the enzyme. 6. O-Phospho-L-serine was isolated from the acid-hydrolysis product of beta-glucosidase A but not from that of beta-glucosidase D. 7. Reduction and carboxamidomethylation of the various forms of beta-glucosidase gave only one enzymically inactive protein with an Mr of 10,000-11,000. 8. After partial succinylation (3-carboxypropionylation) of beta-glucosidase D at pH 5.0 and removal of the precipitated protein formed, the supernatant solution contained beta-glucosidase components similar to the other molecular forms (A, B and C) and an aggregate (beta-glucosidase Xs) that gave a positive result in the alkaline hydroxylamine test, whereas N-succinylated beta-glucosidase D, an aggregate (form Xp) that behaved like beta-glucosidase Xs and traces of forms A, B and C were found by gel filtration of the solution of the precipitate solubilized at neutral pH (7.0-7.7). 9. These observations are discussed in terms of the proposed octameric structure of beta-glucosidase A based on the result of electron microscopy [Umezurike (1975) Biochem. J. 145, 361-368].

New steroid haptens for radioimmunoassay: synthesis of steroids substituted with thioether or ester linkages at the 2 alpha-position

Haptens with bridge at the 2-position have not yet been explored. Radioimmunoassays with antibodies directed against 2 alpha-alkyl bridged steroid haptens are expected to be highly specific due to greater topographical exposure and similarity in conformation to the native steroid. The 2 alpha-alkyl bridged haptens were synthesized by first adding a cyclopropane ring to 2-methylene-4-en-3-one. Selective opening of the three-membered ring with trimethyl silyl iodide and transformation of the iodo group gave a carbocyclic acid, the desired analog for conjugation with protein.

Tumor reactive cis-aconitylated monoclonal antibodies coupled to daunorubicin through a peptide spacer are unable to kill tumor cells

Antibody-drug conjugates containing a linkage susceptible to lysosomal hydrolases were constructed by coupling peptide-daunorubicin (DNR) derivatives to MAb. Using a modification in the method of Trouet et al, peptide derivatives of DNR containing the sequences Ala-Leu and Ala-Leu-Ala-Leu linked to drug via their carboxy terminus were prepared. Cleavage of these derivatives by lysosomal enzymes resulting in the release of free DNR was demonstrated. Human antitumor MAb were derivatized with either succinic anhydride or cis-aconitic anhydride to introduce spacer arms for coupling. Binding studies showed that MAb with a decrease of 12-20 amino groups retained greater than 70% of their immunoreactivity, a level deemed acceptable for constructing conjugates. Derivatized and native MAb were conjugated to peptide-DNR via a carbodiimide mediated reaction. None of the conjugates displayed cytotoxicity toward target tumor cell lines in vitro.

Selective chemical modification of cytochrome P-450SCC lysine residues. Identification of lysines involved in the interaction with adrenodoxin

Selective chemical modification of cytochrome P-450SCC has been carried out with lysine-modifying reagents. Modification of cytochrome P-450SCC with succinic anhydride was shown to result in loss of its ability to interact with intermediate electron transfer protein - adrenodoxin. To identify amino acid residues involved in charge-ion pairing with complementary carboxyl groups of adrenodoxin, cytochrome P-450SCC complex with adrenodoxin was modified with succinic anhydride. Adrenodoxin was then removed and cytochrome P-450 was additionally modified with isotopically labelled reagent. Subsequent chymotryptic hydrolysis of [14C]succinylated cytochrome P-450SCC and separation of digest obtained by combining various types of HPLC resulted in seven major radioactive peptides. The amino acid sequence of the peptides was determined by microsequencing. The major amino groups modified with radioactive succinic anhydride were found to be at Lys-73, -109, -110, -126, -145, -148 and -154 in the N-terminal sequence of cytochrome P-450SCC molecule and at Lys-267, -270, -338 and -342 in the C-terminal sequence. The role of electrostatic interactions in fixation of cytochrome P-450SCC complex with adrenodoxin is discussed.

[Study of the role of lysine residues of the cholesterol hydroxylating cytochrome P-450 by a method of chemical modification]

Chemical modification of cytochrome P-450scc by lysine-specific reagents has been performed. Modification of the hemoprotein was shown to result in the loss of its ability to interact with adrenodoxin. With a view of identifying lysine residues involved in the interaction with adrenodoxin, cytochrome P-450scc was modified by succinic anhydride in the presence of adrenodoxin. After the removal of ferredoxin, the modification was performed with the use of a radioactively labeled reagent. Subsequent hydrolysis of the succinic hemoprotein by chymotrypsin and separation of the peptides obtained by high pressure liquid chromatography resulted in the isolation of seven chymotryptic peptides containing labeled lysine residues. These amino acid sequences were identified. The role of lysine residues of cytochrome P-450scc in complex formation with adrenodoxin is discussed.

Evidence for the overestimation of molecular masses of proteins after chemical modification and chemical crosslinks on sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE)

Human trypsin inhibitor (home prepared), lactalbumin, trypsinogen, carbonic anhydrase, and bovine serum albumin were submitted to succinylation and their molecular masses were determined by SDS-PAGE according to the method of Weber and Osborn (1969 J. Biol. Chem. 244, 4406) before and after chemical modification. High estimates of their molecular masses were obtained. The monomer and dimer of arrowhead inhibitor proteinase-B (Chinese vegetable legume) obtained after chemical crosslink(s) were also submitted to SDS-PAGE and their apparent molecular masses were also determined and compared to the native arrowhead inhibitor proteinase-B. Abnormally high estimates of their molecular masses were obtained. Our results agree with those in the literature.

Solid-phase synthesis of oligoribonucleotides using 9-fluorenylmethoxycarbonyl (Fmoc) for 5'-hydroxyl protection

Efficient solid-phase synthesis of a series of oligoribonucleotides of up to 20 residues is described that utilises the 9-fluorenylmethoxycarbonyl group (Fmoc) for 5'-protection and 4-methoxytetrahydropyran-4-yl (Mthp) for 2'-protection of ribonucleotide monomers and a phosphoramidite coupling procedure. The Fmoc group is removed after each coupling step by treatment with 0.1M DBU in acetonitrile. Oligoribonucleotides are isolated in 2'-protected form in good yield and shown to be readily and efficiently deprotected by mild acidic treatment.

The molecular basis of granuloma formation in schistosomiasis. II. Analogies of a T cell-derived suppressor effector factor to the T cell receptor

During Schistosoma mansoni infection, Ts cells regulate granulomatous modulation via antigenically and genetically restricted suppressor inducer and suppressor effector factors. The T suppressor effector factor (TseF) directly suppresses granuloma formation both in vitro and in vivo. In this study, we probe the molecular basis of these TseF properties. Using techniques of heterodimeric chain reduction with DTT and in vitro functional complementation, chimeric molecules were constructed. By analyzing genetic restrictions, antigenic specificities, and phenotypic markers, the contributions of the component chains to 72 kDa TseF reactivity were determined. One chain bore an Ag receptor and imparted antigenic specificity. The other chain bore an IJ determinant, a TCR beta-chain allotypic determinant, a suppressor effector phenotypic determinant, and imparted functional genetic restriction. Functional activity required covalent, probably sulfhydryl mediated, linkage as succinylation prevented the separated component chains from reconstituting functional activity. Additional studies demonstrated that anti-serum directed against either the T cell receptor or the T3 epsilon-chain could abrogate functional activity. However, TseF bore no T3 epsilon-chain phenotypic marker per se suggesting that TseF effects T lymphocytes via transmembrane signal transduction. These studies suggest that a regulatory network is operative in granuloma modulation. This regulatory network is mediated by a soluble TseF that bears significant structural homologies to the classic TCR.

Noninvolvement of surface lysine residues of bovine serum albumin in bilirubin binding

Interaction of bilirubin with bovine serum albumin and its five succinylated forms was studied using fluorescence spectroscopy at two different ionic strengths i.e., 0.15 and 1.0 respectively. Affinity constant was found to be 1.8 x 10(7) litres/mole at 0.15 ionic strength which decreased to 4.4 x 10(6) litres/mole after 87% succinylation. On increasing ionic strength to 1.0, there was a slight decrease in affinity constant for native albumin. However, affinity constant remained same in 55 and 87% modified albumins at high ionic strength. These results suggest noninvolvement of surface lysine residues in bilirubin albumin complex.

Introduction of 5'-terminal functional groups into synthetic oligonucleotides for selective immobilization

Oligodeoxyribonucleotides terminating in a 5'-primary amine group are synthesized using solid-phase supported phosphoramidite chemistry. The 5'-terminal amine group in the deprotected oligomers is further derivatized with either succinic anhydride to give 5'-carboxylic acid or with dithiobis(succinimidylpropionate) followed by treatment with dithioerythritol to produce 5'-thiol-terminated oligonucleotides. The 5'-thiol-terminated oligonucleotides are selectively immobilized on solid supports containing either p-chloromercuribenzoate or 2,2'-dithiobis(5-nitropyridine) activated thiol groups.

Effects of chemical modifications on the surface- and protein-binding properties of the light chain of human high molecular weight kininogen

The light chain of kallikrein-cleaved human high molecular weight kininogen is solely responsible for its cofactor activity in blood clotting. Sequencing of the NH2-terminal region of the light chain reported herein identified the third kallikrein cleavage site of high molecular weight kininogen as Arg-437. The co-factor activity of high molecular weight kininogen consists of the capacity to bind to negatively charged surfaces and to factor XI or prekallikrein. Chemical modification of the histidines by either photooxidation or ethoxyformic anhydride affected the equivalent of 14-16 of 23 histidines available and resulted in over 90% loss in procoagulant activity. The modified protein had drastically reduced surface- and zinc-binding capacity, but it bound successfully to either factor XI or prekallikrein. In contrast, modification of two carboxyl groups, which led to approximately 80-90% loss of procoagulant activity, seriously compromised protein binding but left surface binding unaffected. All 3 tryptophans were modified at pH 4.0 with N-bromosuccinimide with a 70% reduction in procoagulant activity, but only 1 tryptophan was available for reaction at pH 7.35, resulting in a 50% loss in activity. Tryptophan modification at acidic pH affected protein binding but did not modify surface or zinc binding. Modification of both available tyrosine and 9 of 18 available lysine residues did not have a significant effect on the procoagulant activity of the light chain. These studies indicate that histidines participate in surface binding and that free carboxyl groups and tryptophan side chains are involved in binding of high molecular weight kininogen to other clotting factors.

A correlation between changes in conformation and molecular properties of bovine serum albumin upon succinylation

Using succinic anhydride, six succinylated derivatives of bovine serum albumin having percent modification in the range of 23-87% were prepared and their physicochemical and immunological properties were studied. Measurements of Stokes radius, frictional ratio, UV spectra, solvent perturbation, solubility, and immunological cross-reactivity against anti-bovine serum albumin antiserum revealed that the protein undergoes gradual changes in its native conformation with increase in the degree of succinylation. These changes were less marked below 50% modification but became pronounced above 50% modification. However, even the maximally modified preparation (87%) contained a significant amount of folded structure. Interestingly, though the measurements of various molecular properties revealed significant changes in 23-49% modified preparations, the solubility parameters for these preparations which were obtained at high ionic strength were indistinguishable from those of the native protein. The various results taken together suggest that at lower degrees of chemical modification, the conformational changes were produced mainly because of an increase in electrostatic free energy, whereas at higher degrees of modification, steric hindrance in addition to the electrostatic factor seems to make a substantial contribution to the conformational changes in the modified proteins.