Cavities formed using cyclic tetrapeptides (CTPs) or heat-induced conformers act as templates for cyclization; the cavities bind to linear tetrapeptides and enforce turn conformations to enhance cyclization to constrained CTPs.

Serum is a readily available source for noninvasive studies in clinical research, but it contains abundant proteins such as albumin and immunoglobulin G that can hinder the presence of low-abundant proteins as well as decrease sample loading capacity of analytical methods. Therefore, depletion of these two proteins is required to observe low-abundance serum proteins. Molecularly imprinted polymers are template-induced artificial antibodies with the ability to recognize and selectively bind the target molecule. In this study, artificial albumin and immunoglobulin G antibodies were developed by using two epitopes of human serum albumin and immunoglobulin G as templates. Acrylic acid, acrylamide, and N-acryl tyramine were the corresponding monomers; N,N'-ethylene bisacrylamide served as a cross-linker, and cellulosic fibers were used as a supporting matrix. The adsorption capacity of these artificial antibodies was 15.2 mg, 10 mg, and 15 μL per gram for human serum albumin, immunoglobulin G, and human serum, respectively. The dissociation constant (Kd ) of these artificial antibodies toward the human serum albumin and immunoglobulin G was 1 μM and 0.6 μM, respectively. The biomimetic properties of these artificial antibodies, coupled with their economical and rapid production, high specificity and their reusability, make them attractive for protein separation and analysis.

A complementary peptide separation and purification system, using a novel, artificial, affinity-type extraction material, is described. Cellulose paper was first coated with a 3-methacryloxypropyltrimethoxysilane (MPS) layer, followed by imprinting with peptides, to form an approximately 2-µm layer of film (molecularly imprinted polymer film; MIPF) on both sides and resulted in an increased affinity toward the corresponding template as well as to matched polypeptides. MIPF-cellulose paper (MIFC) was immersed in 2% peptide solution (acetonitrile/water) for the sorption of targeted-peptides at room temperature for an hour in a 96-well microtiter plate. Desorption of targeted-peptides from the MIPF-and NIPF (non-imprinted polymeric film)-coated filter papers was nearly complete (~99%) in two desorptions of 10 min using 5% acetic acid in water. Clean extracts of targeted-peptides were obtained demonstrating the suitability of MIPF-coated filter papers for the extraction or analysis of biological samples. To compare their extraction characteristics under various conditions, analyses were carried out by an enzyme-linked immunosorbent assay (ELISA) microplate reader as peptide-detecting/peptide-capturing microarrays. In load ability studies using acetonitrile/water, peptide masses up to 100 µg could be applied onto a piece of MIPF coated filter paper (0.7 cm in diameter). ArticleTai et al. Scheme II Operation of MIFC for the extraction of peptide Fig. 2. Scatchard plot for the binding of the Phe-Phe-Phe-Phe to MIFC. Data points are the average of triplicates.

Based on the fabrication of molecularly imprinted polymeric film on cellulose paper (MIFC), we have developed a robotic system for homodetic tetrapeptide cyclization. We constructed molecularly imprinted polymeric film (MIPF) on cellulose paper as the non‐covalent auxiliary to assist cyclic tetrapeptide (CTP) formation. Tetrapeptides were bound by their hydrophobic interaction with MIFC. With the help of MIFC and a coupling reagent, quantitative synthesis of CTPs was achieved conveniently for various tetrapeptides. The syntheses of cyclic tetrapeptide (CTP) could also be facilitated using the MIFC induced from CTP or other tetrapeptides with partially matched sequences.