The enantioselective immunoaffinity extraction of an optically active ibuprofen-modified peptide fragment

Central Chirality and Axial Chirality Recognition of the Enantioselective Antibodies to Herbicide Metolachlor

Enantioselective antibodies have emerged as efficient tools in the field of chiral chemical detection and separation. However, it is complicated to obtain a highly stereoselective antibody due to the unclear recognition mechanism. In this study, the hapten of metolachlor was synthesized and enantio-separated. The absolute configuration of the four haptens obtained was identified by the computed and experimental electronic circular dichroism comparison. Five polyclonal antibodies against the Rac-metolachlor and its enantiomers were generated by immunization. The cross-activity of all the 5 antibodies with 44 structural analogues, including metolachlor enantiomers, was tested. It demonstrated that antibodies have higher specificity to recognize central chirality than axial chirality. Especially, αRR-MET-Ab exhibited excellent specificity and stereoselectivity. Accordingly, 3D-QSAR models were constructed and revealed that paired stereoisomers exhibited opposite interactions with the antibodies. It is the first time that the antibodies against four stereoisomers were prepared and analyzed, which will be conducive to the rational design of the stereoselective antibodies.

Quantitative analysis of biomarkers, drugs and toxins in biological samples by immunoaffinity chromatography coupled to mass spectrometry or tandem mass spectrometry: A focused review of recent applications

Immunoaffinity chromatography (IAC), mass spectrometry and especially tandem mass spectrometry (MS/MS) represent the most efficient and reliable analytical techniques for specific isolation, unequivocal identification and accurate quantification of numerous natural and synthetic substances in biological samples. This review article focuses on the combined use of these outstanding methodologies in basic and clinical research and in life sciences for the quantitative analysis of low- and high-molecular mass biomarkers, drugs and toxins in urine, plasma or serum samples, in tissue and other biologicals systems published in the last decade. The analytes discussed in some detail include the biomarkers of oxidative stress 15(S)-8-iso-prostaglandin F(2alpha) {15(S)-8-iso-PGF(2alpha)} and 3-nitrotyrosine, the major urinary metabolite of the lipid mediators cysteinyl leukotrienes, i.e., the leukotriene E(4) (LTE(4)), melatonin, and the major collagen type II neoepitope peptide in human urine.

Development of immunoaffinity restricted access media for rapid extractions of low-mass analytes

Restricted access media using antibodies as immobilized ligands were developed for the rapid and selective capture of small analytes by immunoextraction, giving rise to materials referred to as immunoaffinity restricted access media (IA-RAM). To make such a material, intact antibodies for the desired target were first immobilized onto porous silica, with antibodies at or near the outer surface of the support then being treated with papain (or a related agent) to release and remove their binding domains. The result was a support in which only antibodies deep within the pores remained intact and able to bind to the target. Items evaluated in the development of such media included the immobilization method used for the antibodies, the pore size of the support, and the amount of papain and time that were used for support treatment. A theoretical model was also developed to describe the extent of binding domain removal based on the measured polypeptide content of the IA-RAM support before and after treatment with papain. The final optimized conditions for making the IA-RAM supports were used to prepare columns that contained antifluorescein antibodies. Injections of fluorescein and fluorescein-labeled bovine serum albumin onto these IA-RAM columns gave selective and quantitative extraction of fluorescein in 1-2 s. This approach can be used with other antibodies and low-mass targets and should be valuable for such applications as the rapid separation of drugs from drug-protein complexes or the isolation of labeled/modified peptides from intact proteins that contain the same modification or label.

Enantioselective immunorecognition of protein modification with optically active ibuprofen using polyclonal antibody

Formation of covalently bound protein adducts with 2-arylpropionic acids (2-APAs) has been proposed as a possible explanation for hypersensitivity and toxic responses to chiral carboxylic acid drugs. To identify the cellular proteins chemically modified with optically active (S)-ibuprofen, we generate polyclonal antibodies by immunizing rabbits with immunogen coupled to bovine serum albumin (BSA) via the spacer of 4-aminobutyric acid. The resulting antibodies largely cross-reacted with N-alpha-(t-butoxycarbonyl)--(S)-ibuprofenyl lysine as well as with the conjuguated (S)-ibuprofen with glycine and taurine and unconjugated (S)-ibuprofen, enabling enantioselective detection of (S)-ibuprofen residues anchored on ovalbumin molecules, introduced by the reaction of the ibuprofen p-nitrophenyl ester. Furthermore, immunoblotting with an antibody allows the enantioselective detection of (S)-ibuprofen-introduced glutathione-S-transferase (GST). These results indicate that the developed method will be useful for monitoring the generation and localization of protein covalently bound with (S)-ibuprofen, which may be the cause of ibuprofen-induced toxicity.

Isolation of antigens and antibodies by affinity chromatography

Antibody-antigen binding constants are commonly strong enough for an effective affinity purification of antibodies (by immobilized antigens) or antigens (by immobilized antibodies) to work out a straightforward purification method. A drawback is that antibodies are large protein molecules and subject to denaturation under conditions required for the elution from the complex. Structures of antigens can vary but usually antigens are also equally subject to similar problems. The lability of the components can sometimes make the procedure sophisticated, but usually in all cases it is possible to find a satisfactory approach. In certain cases, specific interactions of the Fc part of antibodies are more facile to exploit for their purification.

Immuno-based sample preparation for trace analysis

Immuno-based sample preparation techniques are based upon molecular recognition. Thanks to the high affinity and high selectivity of the antigen-antibody interaction, they have been shown to be a unique tool in the sampling area. Immuno-based sample preparation methods include the widely encountered immunoaffinity extraction sorbents, so-called immunosorbents, as well as membrane-baed or ultrafiltration techniques. This review describes the new developments and applications that have occurred in recent years with emphasis on (i) the antigen-antibody interactions, (ii) and their importance for the properties and use of immunosorbents, (iii) multiresidue extractions, (iv) the on-line coupling to chromatographic or electrophoretic separations, and (v) the high potential for improving MS detection. The recent use of artificial antibodies for sample pretreatment, so-called molecularly imprinted polymers, is also described.

Separation and Determination of Diastereomeric Flurbiprofen Acyl Glucuronides in Human Urine by LC/ESI-MS with a Simple Column-Switching Technique

Endogenous and exogenous compounds having a carboxyl group, such as alpha-arylpropionic acid derivatives, undergo a phase II metabolic reaction to produce an amino acid conjugate through the acyl CoA thioester as well as the acyl glucuronide. It was previously shown that flurbiprofen, one of the nonsteroidal anti-inflammatory drugs, is not subjected to activation of the carboxyl group by the CoA thioester ligase, suggesting that acyl glucuronidation is the main phase II metabolic pathway. Recent observations, however, have demonstrated that the nonenzymatic formation of a covalently protein-bound drug, which is produced by the action of the acyl glucuronide, may cause hypersensitive reactions. Accordingly, a reliable method to measure diastereomeric flurbiprofen glucuronides in human biological fluids is required. In this study, we describe a liquid chromatographic/mass spectrometric method with a simple column switching technique to determine diastereomeric flurbiprofen acyl glucuronides in human urine specimens. The optimal conditions for the electrospray ionization were established based on the effects of orifice and ring lens voltages as well as mobile phase additives. The proposed method applied to urine specimens demonstrates high accuracy and reproducibility for the determination of flurbiprofen glucuronides in a quantitative range from 0.74 to 146.5 microg/mL, with a detection limit of 7.4 pg (17.6 fmol)/injection of S-flurbiprofen glucuronide, at a signal-to-noise ratio of 10 under the selected ion-monitoring mode. The urinary concentration of R-flurbiprofen glucuronides in healthy subjects determined by the proposed method were 6.8-29.4 microg/mL, and those values were slightly higher than that of S-flurbiprofen glucuronides (3.9-18.0 microg/mL).