Sulfate conjugation of benzo[alpha]pyrene metabolites and derivates

Sulfate conjugation of benzo[alpha]pyrene(BP) metabolites and derivatives was studied. The reaction sequence consisted of two steps; activation of sulfate ion to 3'-phosphoadenosine-5'-phosphosulfate and transfer of the activated sulfate to the BP-derivatives. Both reactions were carried out by enzymes located in the rat liver 105 000 g supernatant. The reactions required MgCl2. Phenol and quinone derivatives were generally good substrates for sulfate conjugation and different reactivities were observed with the dihydrodiol derivatives. Sulfate conjugates were more polar than their parent BP-derivatives and except for quinone conjugates were easily extracted with ethyl acetate. The role of sulfate conjugation in BP carcinogenesis is discussed.     

Cleavage of disulfide-linked fetuin-bisphosphonate conjugates with three physiological thiols

An effective therapeutic agent for treatment of bone diseases is expected to exhibit a high affinity to bone. Conjugating proteins to bisphosphonates (BPs), a class of molecules with an exceptional affinity to bone mineral hydroxyapatite (HA), is a feasible means to impart such a bone affinity. Protein-BP conjugates with cleavable linkages, which allow protein release from the mineral, are preferable over conjugates with stable linkages. To this end, 2-(3-mercaptopropylsulfanyl)-ethyl-1,1-bisphosphonic acid (thiolBP) was conjugated onto fetuin, a model protein, using N-succinimidyl-3-(2-pyridyldithio)propionate to create disulfide-linked conjugates. Although the fetuin-thiolBP conjugates were stable under aqueous conditions, the disulfide linkage was readily cleaved in the presence of the physiological thiols l-cysteine, dl-homocysteine, and l-glutathione. dl-Homocysteine exhibited the highest cleavage of the disulfide linkage among these thiols. The imparted bone affinity as a result of thiolBP conjugation, as assessed by HA binding in vitro, was eliminated upon cleavage of the disulfide linkage. The cleavage of the conjugates bound to HA was as effective as the conjugate cleavage in solution, and even more so at high concentrations of l-glutathione. In conclusion, disulfide-linked fetuin-thiolBP conjugates exhibited a high affinity to HA, which was readily lost upon cleavage with thiols found in physiological milieu.     

A Universal Approach to Prepare Reagents for DNA-Assisted Protein Analysis

The quality of DNA-labeled affinity probes is critical in DNA-assisted protein analyses, such as proximity ligation and extension assays, immuno-PCR, and immuno-rolling circle amplification reactions. Efficient, high-performance methods are therefore required for isolation of pure conjugates from reactions where DNA strands have been coupled to antibodies or recombinant affinity reagents. Here we describe a universal, scalable approach for preparing high-quality oligonucleotide-protein conjugates by sequentially removing any unconjugated affinity reagents and remaining free oligonucleotides from conjugation reactions. We applied the approach to generate high-quality probes using either antibodies or recombinant affinity reagents. The purified high-grade probes were used in proximity ligation assays in solution and in situ, demonstrating both augmented assay sensitivity and improved signal-to-noise ratios.     

Bisphosphonate conjugation to proteins as a means to impart bone affinity

Growth factors are endogenous proteins capable of stimulating new bone formation, but their clinical benefit for systemic stimulation of bone mass has not been demonstrated. The critical challenge is to deliver a significant dose of the proteins to bone after intravenous injection. This challenge may be overcome by derivatizing proteins with ligands that exhibit a high bone affinity (e.g., bisphosphonates). To demonstrate the feasibility of this approach, 1-amino-1,1-diphosphonate methane (aminoBP) was conjugated to a model protein, albumin. The conjugation was performed by (1) converting the amino group of aminoBP to a thiol group using 2-iminothiolane, (2) derivatizing the albumin amino groups with a thiol-reactive sulfosuccinimidyl-4-(N-maleimidomethyl)-1-cyclohexane carboxylate, and (3) reacting the derivatized albumin with thiolated aminoBP. Typically, 1-4 aminoBP molecules per albumin were obtained. The conjugated albumin exhibited a high affinity to hydroxyapatite that was proportional to the extent of conjugation. The conjugates were shown to exhibit a high affinity to bone matrix in vitro in a serum-containing medium. Once bound to bone matrix, the conjugates were found to desorb more slowly than the unmodified albumin, especially from bone whose organic matrix was removed by ashing. In conclusion, conjugation of bisphosphonates to albumin was shown to impart a high bone affinity to the protein, and such conjugates can be potentially targeted to bone.     

Peroxidase and fluorescein isothiocyanate as antibody markers. A quantitative comparison of two peroxidase conjugates prepared with glutaraldehyde or periodate anda fluorescein conjugate.

Batches of rabbit anti-human immunoglobulin G antibodies were labeled either with horseradish peroxidase, using the two-step glutaraldehyde method or the periodate method, or with fluorescein isothiocyanate (FITC). The peroxidase conjugates were isolated by chromatography using two different gel types. The five types of conjugates thus obtained were standardized to the same amount of rabbit immunoglobulin G. The antibody activity, as estimated by means of single radial immunodiffusion and passive hemagglutination, and the enzyme activity, determined with orthodianisidine, were compared. The ultimate dilutions and absolute amounts of the five conjugates giving positive reactions were determined in direct and indirect immunohistochemical tests, using both cryostat sections of skin and the agarose bead model system. It appeared that during the peroxidase conjugation procedures there was a considerable loss of abtibody and enzyme activity, whereas in the FITC conjugation procedure the antibody activity remained intact. Neverthe less, peroxidase conjugates prepared with glutaraldehyde still gave positive staining reactions in equal or somewhat higher dilutions than the fluorescin conjugate did. The peroxidase conjugates prepared with periodate could not be diluted to the same extent. For the detection of antibodies by indirect immunohistochemical methods, the peroxidase conjugate, prepared with glutaraldehyde, was comparable to the FITC conjugate. The peroxidase conjugate, prepared with periodate, was less effective.     

Immobilization-stabilization of proteins on nanofibrillated cellulose derivatives and their bioactive film formation

In a number of different applications for enzymes and specific binding proteins a key technology is the immobilization of these proteins to different types of supports. In this work we describe a concept for protein immobilization that is based on nanofibrillated cellulose (NFC). NFC is a form of cellulose where fibers have been disintegrated into fibrils that are only a few nanometers in diameter and have a very large aspect ratio. Proteins were conjugated through three different strategies using amine, epoxy, and carboxylic acid functionalized NFC. The conjugation chemistries were chosen according to the reactive groups on the NFC derivatives; epoxy amination, heterobifunctional modification of amino groups, and EDC/s-NHS activation of carboxylic acid groups. The conjugation reactions were performed in solution and immobilization was performed by spin coating the protein-NCF conjugates. The structure of NFC was shown to be advantageous for both protein performance and stability. The use of NFC allows all covalent chemistry to be performed in solution, while the immobilization is achieved by a simple spin coating or spreading of the protein-NFC conjugates on a support. This allows more scalable methods and better control of conditions compared to the traditional methods that depend on surface reactions.     

Preparation of bioconjugates by solid-phase conjugation to ion exchange matrix-adsorbed carrier proteins

A solid-phase conjugation method utilizing carrier protein bound to an ion exchange matrix was developed. Ovalbumin was adsorbed to an anion exchange matrix using a batch procedure, and the immobilized protein was then derivatized with iodoacetic acid N-hydroxysuccinimid ester. The activated protein was conjugated with glutathione, the conjugation ratio determined by acid hydrolysis, and amino acid analysis performed with quantification of carboxymethyl cysteine. Elution of conjugates from the resin by a salt gradient revealed considerable heterogeneity in the degree of derivatization, and immunization experiments with the eluted conjugates showed that the more substituted conjugates gave rise to the highest titers of glutathione antibodies. Direct immunization with the conjugates adsorbed to the ion exchange matrix was possible and gave rise to high titers of glutathione antibodies. Conjugates of ovalbumin and various peptides were prepared in a similar manner and used for production of peptide antisera by direct immunization with the conjugates bound to the ion exchanger. Advantages of the method are its solid-phase nature, allowing fast and efficient reactions and intermediate washings, and the ability to release conjugates from the solid phase under mild conditions.     

Chemoselective oxime and thiazolidine bond formation: a versatile and efficient route to the preparation of 3'-peptide-oligonucleotide conjugates

Oligonucleotides carrying an aldehyde moiety at the 3'-end were synthesized by the oxidation of a 1,2-diol precursor. These were coupled to peptides bearing a cysteine residue for thiazolidine formation and an aminooxy group for oxime formation. The conjugation reaction proved very efficient and selective, thereby allowing the preparation of 3'-peptide-oligonucleotide conjugates in good yield. The conjugation was achieved in aqueous solution without using any protection strategy. Moreover, the present approach neither requires the use of peptide in excess nor changes the hybridization properties of the conjugates.     

Bioconjugation of therapeutic proteins and enzymes using the expanded set of genetically encoded amino acids

The last decade has witnessed striking progress in the development of bioorthogonal reactions that are strictly directed towards intended sites in biomolecules while avoiding interference by a number of physical and chemical factors in biological environment. Efforts to exploit bioorthogonal reactions in protein conjugation have led to the evolution of protein translational machineries and the expansion of genetic codes that systematically incorporate a range of non-natural amino acids containing bioorthogonal groups into recombinant proteins in a site-specific manner. Chemoselective conjugation of proteins has begun to find valuable applications to previously inaccessible problems. In this review, we describe bioorthogonal reactions useful for protein conjugation, and biosynthetic methods that produce proteins amenable to those reactions through an expanded genetic code. We then provide key examples in which novel protein conjugates, generated by the genetic incorporation of a non-natural amino acid and the chemoselective reactions, address unmet needs in protein therapeutics and enzyme engineering.     

Bifunctional PAMAM dendrimer conjugates of folic acid and methotrexate with defined ratio

Our group previously developed a multifunctional, targeted cancer therapeutic based on Generation 5 (G5) polyamidoamine (PAMAM) dendrimers. In those studies we conjugated the targeting molecule folic acid (FA) and the chemotherapeutic drug methotrexate (MTX) sequentially. This complex macromolecule was shown to selectively bind and kill KB tumor cells that overexpress folate receptor (FR) in vitro and in vivo. However, the multistep conjugation strategy employed in the synthesis of the molecule resulted in heterogeneous populations having differing numbers and ratios of the functionally antagonistic FA and MTX. This led to inconsistent and sometimes biologically inactive batches of molecules, especially during large-scale synthesis. We here resolved this issue by using a novel triazine scaffold approach that reduces the number of dendrimer conjugation steps required and allows for the synthesis of G5 conjugates with defined ratios of FA and MTX. Although an unoccupied γ-glutamyl carboxylate of FA has been previously suggested to be nonessential for FR binding, the functional requirement of an open α-carboxylate still remains unclear. In an attempt to also address this question, we have synthesized isomeric FA dendrimer conjugates (α-carboxyl or γ-carboxyl linked). Competitive binding studies revealed that both linkages have virtually identical affinity toward FR on KB cells. Our studies show that a novel bifunctional triazine-based conjugate G5-Triazine-γMTX-αFA with identical numbers of FA and MTX binds to FR through a polyvalent interaction and induces cytotoxicity in KB cells through FR-mediated cellular internalization, inducing higher toxicity as compared to conjugates synthesized by the multistep strategy. This work serves as a proof of concept for the development of bifunctional dendrimer conjugates that require a defined ratio of two functional molecules.     

The Biochemistry of Drug Metabolism – An Introduction

This review continues a general presentation of the metabolism of drugs and other xenobiotics begun in three recent issues of Chemistry & Biodiversity. The present Part is dedicated to reactions of conjugation, namely methylation, sulfonation, and phosphorylation, glucuronidation and other glycosidations, acetylation and other acylations, the formation and fate of coenzyme A conjugates, glutathione conjugation, and the reaction of amines with carbonyl compounds. It presents the many transferases involved, their nomenclature, relevant biochemical properties, catalytic mechanisms, and the reactions they catalyze. Nonenzymatic reactions, mainly of glutathione conjugation, also receive due attention. A number of medicinally, environmentally, and toxicologically relevant examples are presented and discussed.     

3-oxo-α-ionol,vomifoliol and roseoside in Vitis vinifera fruit

3-Oxo-β-ionol, vomifoliol and dehydrovomifoliol were identified for the first time in fruit from Vitis vinifera. The last named compound was mainly present free in the juice while the others existed predominantly as conjugates. In the case of vomifoliol, the conjugation was with glucose, i.e. as roseoside. Hydrolytic studies on 3-oxo-α-ionol and vomifoliol gave a range of compounds which have been recognized as fruit and plant products.     

94个氨基酸的前列腺分泌蛋白与TNFα衍生物的协同抗肿瘤作用(英文)

体外研究显示,重组PSP94与重组TNFα衍生物11a(rhTNFαDlla)有协同抗前列腺癌的作用。将编码这两种蛋白的基因与真核表达载体pcDNA30重组,构建成pcDNAPSP94TNFαDlla真核表达质粒,两基因中间通过一个编码6个氨基酸的人工接头连接。在体外,对pcDNAPSP94TNFαDlla质粒表达PSP94TNFαDlla蛋白的生物学活性鉴定表明,该蛋白即具有PSP94抑制前列腺癌细胞生长的活性,又具有TNFαDlla对L929细胞的细胞毒作用。肌肉注射该质粒DNA,注射后第9天血液中可检测到目的蛋白的表达,目的蛋白浓度的高峰期约在注射后第14天,第25天仍可检测到目的蛋白的表达。该质粒DNA以50μg只的量给人前列腺癌裸鼠模型骨四头肌内注射,同时设pcDNAPSP94、pcDNATNFαDlla、pcDNA30空载体和生理盐水对照组。注射后第20天处死动物,抑瘤率分别为:pcDNAPSP94TNFαDlla组24%,pcDNAPSP94组19%,pcDNATNFαDlla组瘤体大小与生理盐水组无明显差异。以同样方法给药,pcDNAPSP94TNFαDlla质粒DNA对小鼠Lweis肺癌的抑制率31%,是pcDNAPSP94组抑瘤率的22倍,是pcDNATNFαDlla组抑瘤率的21倍。提示,PSP94与TNF具有协同抗肿瘤的作用 。     

New ferrocene containing peptide conjugates: synthesis and effect on human leukemia (HL-60) cells

Data reported in this article describe the synthesis of Arg-rich oligopeptide conjugates of ferrocenecarboxylic acid on solid support with two different strategies and for the first time, the successful preparation of peptide conjugates of ferrocenylacrylic acid in solution. The antitumor effect of conjugates was analyzed by MTT assay in vitro. We demonstrated that ferrocenylacrylic acid possessing an enone (--CH==CH--CO--) moiety exhibited remarkable antiproliferative effect against human leukemia cells (HL-60) in vitro, but its effect was not improved by conjugation with hexa- or octaarginines. However, we observed highly increased water-solubility. In contrast, the results provide evidence that conjugation of ferrocenecarboxylic acid to Arg(n) (n = 6, 8) improved not only its water-solubility, but also antitumor effect on human leukemia cells in vitro.     

Characterization of morphine-glucose-6-phosphate dehydrogenase conjugates by mass spectrometry

A key characteristic of the analyte-reporter enzyme conjugate used in the enzyme-multiplied immunoassay technique (EMIT) is the inhibition of the conjugate enzyme upon anti-analyte antibody binding. To improve our understanding of the antibody-induced inhibition mechanism, we characterized morphine-glucose-6-phosphate dehydrogenase (G6PDH) conjugates as model EMIT analyte-reporter enzyme conjugates. Morphine-G6PDH conjugates were prepared by acylating predominantly the primary amines on G6PDH with morphine 3-glucuronide NHS ester molecules. In this study, morphine-G6PDH conjugates were characterized using a combination of methods, including tryptic digestion, immunoprecipitation, matrix-assisted laser desorption ionization mass spectrometry, and electrospray ionization tandem mass spectrometry. Twenty-six conjugation sites were identified. The identified sites all were found to be primary amines. The degree of conjugation was determined to be less than the number of conjugation sites, suggesting heterogeneity within the morphine-G6PDH conjugate population. Two catalytically important residues in the active site (K22 and K183) were among the identified conjugation sites, explaining at least partially the cause of loss of activity due to the coupling reaction.     

A novel one-pot de-blocking and conjugation reaction step leads to process intensification in the manufacture of PEGylated insulin IN-105

Bio-catalytic in vitro multistep reactions can be combined in a single step in one pot by optimizing multistep reactions under identical reaction condition. Using this analogy, the process of making PEGylated insulin, IN-105, was simplified. Instead of taking the purified active insulin bulk powder as the starting material for the conjugation step, an insulin process intermediate, partially purified insulin ester, was taken as starting material. Process intensification (PI) was established by performing a novel de-blocking (de-esterification) of the partially purified insulin ester and conjugation at B-29 Lys residue of B chain with a short-chain methoxy polyethylene glycol (mPEG) in a single-pot reactor. The chromatographic profile at the end of the reaction was found similar irrespective of whether both the reactions were performed sequentially or simultaneously. The conjugated product of interest, IN-105 (conjugation at LysB(29)), was purified from the heterogeneous mixture of conjugated products. The new manufacturing process was deduced to be more simplified and economical in making the insulin conjugates as several downstream purification steps could be circumvented. The physicochemical characteristics of IN-105 manufactured through this economic process was found to be indifferent from the product formed through the traditional process where the conjugation starting material was purified from bulk insulin.     

An antitumor osteotropic agent based on tumor necrosis factor

An osteotropic agent based on the human recombinant tumor necrosis factor alpha (TNF-alpha) has been designed for treatment of bone metastases. It represents a molecular construct containing yeast double- stranded ribonucleic acid (dsRNA) covered by the conjugate of polyanion dextran with TNF-alpha and bisphosphonate alendronic acid. This construct is characterized by the combination of substances possessing antitumor activity (TNF-alpha, dsRNA) and a vector molecule (bisphosphonate) providing tropism to hydroxyapatite, the main mineral component of the bone tissue matrix. The conjugation conditions were optimized and the conjugates of TNF-alpha and alendronic acid with dextran were synthesized. The molecular constructs were obtained by self-assembly, and the resultant complexes were separated by gel filtration on Sepharose CL-6B. The electrophoretic analysis has shown decreased mobility of dsRNA in the complex with the conjugate as compared to mobility of the original dsRNA. This confirms formation of the designed structures. Transmission electron microscopy confirmed the presence of particles with sizes of 30–40 nm in the drug preparation. Evaluation by the sorption/desorption method showed a higher affinity of TNF-alpha conjugates to hydroxyapatite as compared to original TNF-alpha molecules (from 1.0–1.8 mol/L vs. 0.3 mol/L of potassium phosphate buffer for desorption, respectively).     

Light‐microscopic examinations of sperm in several lineages of Carabidae (Insecta: Coleoptera): Implications for the evolution of sperm conjugation

Sperm show marked morphological diversity, but the processes and mechanisms driving this diversity have not been fully elucidated. The beetle family Carabidae represents a potential model system for studying sperm trait evolution. In this study, sperm traits (mainly conjugation and sperm conjugate gross morphology) of 42 species from nine subfamilies of Carabidae were examined using light microscopy. Except in Harpalinae, the type of conjugation was shared by all members of a particular subfamily: in Carabinae, Elaphrinae, Patrobinae and Brachinae, sperm conjugates were observed in which variable numbers of sperm clumped together; in Nebriinae, Cicindelinae and Trechinae, sperm were not organized as conjugates but were present individually; and in Broscinae, both individual sperm and sperm conjugates were observed. In the remaining subfamily, Harpalinae, sperm conjugates were formed in most species, but a loss of conjugation was observed in some species. Mapping the observed sperm traits onto within‐family molecular phylogenetic trees suggested that sperm conjugation was ancestral, with loss of conjugation evolving in several lineages. In sperm conjugates, a short spermatostyle (the axis of sperm conjugates) was the ancestral state, while a long spermatostyle evolved in subsequent lineages. In the long spermatostyle trait, the flexible type without a conspicuous 3D structure was ancestral, while the type with a conspicuous 3D structure, such as the spiral structure, evolved in derived lineages.     

Folic acid delivery by serum proteins: loading efficacy and protein morphology

The loading efficacy of folic acid with serum proteins human serum albumin (HSA), bovine serum albumin (BSA), and beta-lactoglobulin (β-LG) was analyzed and the effect of acid conjugation on protein morphology was determined. Structural analysis showed that folic acid binds HSA, BSA, and β-LG via hydrophilic, hydrophobic, and H-bonding contacts with BSA forming more stable conjugates than HSA and β-LG. Molecular modeling showed the presence of several H-bonding systems, stabilizing acid–protein conjugates. Folic acid conjugation alters protein conformation by major alterations of α-helix and β-sheet. TEM images showed major protein morphological changes inducing protein aggregation upon acid interaction. The results show that serum proteins can deliver folic acid to target molecules.     

Synthesis, characterization, and in vitro activity of dendrimer-streptokinase conjugates

Dendrimer conjugation with low molecular weight drugs has been of increasing interest recently for improving pharmacokinetics, targeting drugs to specific sites, and facilitating cellular uptake. Opportunities for increasing the performance of relatively large therapeutic proteins such as streptokinase (SK) using dendrimers are being explored in this study. Using the active ester method, a series of streptokinase-poly(amido amine) (PAMAM) G3.5 conjugates were synthesized with varying amounts of dendrimer-to-protein molar ratios. Characterization of these conjugates by GPC, IEC, and native-PAGE suggested that the conjugation reaction was successful, resulting in relatively pure SK-dendrimer conjugates. The conjugate made with an equimolar ratio of dendrimer to streptokinase (1:1) exhibited the highest enzymatic activity retention ( approximately 80% retained) that has been reported so far for conjugated streptokinase with macromolecules such as PEG or dextran. SK conjugates with higher streptokinase-to-dendrimer molar ratios (1:10 and 1:20) exhibited lower initial enzymatic activities. However, these conjugates showed sustained thrombolytic activity in plasma, perhaps due to the release of SK from the conjugate. All of the SK conjugates displayed significantly improved stability in phosphate buffer solution, compared to free SK. The high coupling reaction efficiencies and the resulting high enzymatic activity retention achieved in this study could enable a desirable way for modifying many bioactive macromolecules with dendrimers.