Specific Conjugation Research Articles

870 A phase 2 trial of prostate specific membrane antigen antibody drug conjugate (PSMA ADC) in taxane-treated metastatic castration-resistant prostate cancer (MCRPC)

870 A phase 2 trial of prostate specific membrane antigen antibody drug conjugate (PSMA ADC) in taxane-treated metastatic castration-resistant prostate cancer (MCRPC)

Radiolabeling strategies for tumor-targeting proteinaceous drugs.

Owing to their large size proteinaceous drugs offer higher operative information content compared to the small molecules that correspond to the traditional understanding of druglikeness. As a consequence these drugs allow developing patient-specific therapies that provide the means to go beyond the possibilities of current drug therapy. However, the efficacy of these strategies, in particular “personalized medicine”, depends on precise information about individual target expression rates. Molecular imaging combines non-invasive imaging methods with tools of molecular and cellular biology and thus bridges current knowledge to the clinical use. Moreover, nuclear medicine techniques provide therapeutic applications with tracers that behave like the diagnostic tracer. The advantages of radioiodination, still the most versatile radiolabeling strategy, and other labeled compounds comprising covalently attached radioisotopes are compared to the use of chelator-protein conjugates that are complexed with metallic radioisotopes. With the techniques using radioactive isotopes as a reporting unit or even the therapeutic principle, care has to be taken to avoid cleavage of the radionuclide from the protein it is linked to. The tracers used in molecular imaging require labeling techniques that provide site specific conjugation and metabolic stability. Appropriate choice of the radionuclide allows tailoring the properties of the labeled protein to the application required. Until the event of positron emission tomography the spectrum of nuclides used to visualize cellular and biochemical processes was largely restricted to iodine isotopes and 99m-technetium. Today, several nuclides such as 18-fluorine, 68-gallium and 86-yttrium have fundamentally extended the possibilities of tracer design and in turn caused the need for the development of chemical methods for their conjugation.

Polymeric vehicles for topical delivery and related analytical methods

Recently a variety of polymeric vehicles, such as micelles, nanoparticles, and polymersomes, have been explored and some of them are clinically used to deliver therapeutic drugs through skin. In topical delivery, the polymeric vehicles as drug carrier should guarantee non-toxicity, long-term stability, and permeation efficacy for drugs, etc. For the development of the successful topical delivery system, it is of importance to develop the polymeric vehicles of well-defined intrinsic properties, such as molecular weights, HLB, chemical composition, topology, specific ligand conjugation and to investigate the effects of the properties on drug permeation behavior. In addition, the role of polymeric vehicles must be elucidated in in vitro and in vivo analyses. This article describes some important features of polymeric vehicles and corresponding analytical methods in topical delivery even though the application span of polymers has been truly broad in the pharmaceutical fields.

Exploring the Physicochemical Properties of Oxime-Reactivation Therapeutics for Cyclosarin, Sarin, Tabun, and VX Inactivated Acetylcholinesterase

The inactivation of acetylcholinesterase (AChE) by organophosphorus agent (OP) compounds is a serious problem regardless of how the individual was exposed. The reactivation of OP-inactivated AChE is dependent on the OP conjugate, and commonly a specific oxime is better at reactivating a specific OP conjugate than several diverse OP conjugates. The presented research explores the physicochemical properties needed for the reactivation of OP-inactivated AChE. Four different OPs, cyclosarin, sarin, tabun, and VX, were analyzed using the same set of oxime reactivators. A trial descriptor pool of semiempirical, traditional, and molecular interaction field descriptors was used to construct an ensemble of QSAR models for each OP-conjugate pair. Based on the molecular information and the cross-validation ability, individual QSAR models were selected to be part of an OP-conjugate consensus model. The OP-conjugate specific models provide important insight into the physicochemical properties required to reactivate the OP conjugates of interest. The reactivation of AChE inactivated with either cyclosarin or tabun requires the oxime therapeutic to possess an overall polar-positive surface area. Oxime therapeutics for the reactivation of sarin-inactivated AChE are conformationally dependent while oxime reverse therapeutics for VX require a compact region with a highly hydrophilic region and two positively charged pyridine rings.

Several Guaranteed Descent Conjugate Gradient Methods for Unconstrained Optimization

This paper investigates a general form of guaranteed descent conjugate gradient methods which satisfies the descent conditiongkTdk≤-1-1/4θkgk2 θk>1/4and which is strongly convergent whenever the weak Wolfe line search is fulfilled. Moreover, we present several specific guaranteed descent conjugate gradient methods and give their numerical results for large-scale unconstrained optimization.

Anti-Convulsant Drug Valproic Acid in Cancers and in Combination Anti-Cancer Therapeutics

The traditional anti-convulsant drug Valproic Acid (VPA) has been found to be involved in suppressing cancer progression while modulating various cancer-associated signaling pathways. In particular, VPA acts as either a Histone Deacetylase (HDAC) inhibitor or a Notch signaling activator in suppressing tumor growth. VPA is less toxic, and by itself, has limited anti-tumor effects. Thus, VPA has been used as an adjuvant in combination with a variety of other anti-cancer agents for many types of cancers. These combination strategies display potential applications in cancer treatments. In particular, VPA could up-regulate certain G Protein-Coupled Receptors (GPCRs) in some cancer cells. Some of these GPCRs are highly expressed naturally in many cancer cells and these characteristics have been applied towards novel enhanced combination therapeutics with VPA and specific receptor-targeted cytotoxic peptide-drug conjugates.

Membrane Androgen Receptor Down-Regulates c-Src-Activity and Beta-Catenin Transcription and Triggers GSK-3beta-Phosphorylation in Colon Tumor Cells

Background/Aims: Functional membrane androgen receptors (mARs) have recently been described in colon tumor cells and tissues. Their activation by specific testosterone albumin conjugates (TAC) down-regulates the PI-3K/Akt pro-survival signaling and triggers potent pro-apoptotic responses both, in vitro and in vivo. The present study explored the mAR-induced regulation of gene products implicated in the tumorigenic activity of Caco2 colon cancer cells. Methods: In Caco2 human colon cancer cells transcript levels were determined by RT-PCR, protein abundance and phosphorylation by Western blotting and confocal microscopy, as well as cytoskeletal architecture by confocal microscopy. Results: We report time dependent significant decrease in Tyr-416 phosphorylation of c-Src upon mAR activation. In line with the reported late down-regulation of the PI-3K/Akt pathway in testosterone-treated colon tumors, GSK-3beta was phosphorylated at Tyr-216 after long term stimulation of the cells with TAC, a finding supporting the role of this kinase to promote apoptosis. PCR analysis revealed significant decrease of beta-catenin and cyclin D1 transcript levels following TAC treatment. Moreover, confocal laser scanning microscopic analysis disclosed co-localization of beta-catenin with actin cytoskeleton. It is thus conceivable that beta-catenin may participate in the reported modulation of cytoskeletal dynamics in mAR stimulated Caco2 cells. Conclusions: Our results provide strong evidence that mAR activation regulates late expression and/or activity of the tumorigenic gene products c-Src, GSK-3beta, and beta-catenin thus facilitating the pro-apoptotic response in colon tumor cells.

A new multi-host species indirect ELISA using protein A/G conjugate for detection of anti-Toxoplasma gondii IgG antibodies with comparison to ELISA-IgG, agglutination assay and Western blot

Toxoplasma gondii is a zoonotic protozoan parasite which can cause significant disease and losses in livestock and wild animals. It is increasingly recognized as an important foodborne pathogen in a broad range of food animals and products. Effective control strategies require rapid, reliable and cost-effective detection methods for large scale surveys and diagnostic applications in a broad range of warm-blooded animals. To overcome one or more of these shortcomings in the currently available detection methods for T. gondii infection a non-species-specific protein A/G conjugate was used in the development of an indirect ELISA (ELISA-A/G) for the detection of IgG antibodies in serum samples obtained from experimentally infected pigs. The performance of the assay was evaluated using serum samples from pigs, cats, mice and seals with known positive or negative status for T. gondii infection. Results of the ELISA-A/G obtained with pig serum samples were compared with those generated by traditional ELISA using host specific IgG conjugate (ELISA-IgG), modified agglutination test (MAT) and Western blot analysis (WB). Using protein A/G conjugate, comparative analysis of results from 77 samples obtained from T. gondii infected pigs showed excellent agreement between the ELISA-A/G and in-house ELISA-IgG (0.917κ). Similar agreements were also observed when these samples were tested by a commercial ELISA kit (0.816κ), MAT (0.816κ) and WB (0.79κ). A total of 86 serum samples obtained from cats, mice and seals experimentally infected with T. gondii and tested by the ELISA-A/G as well as MAT for the presence of anti-Toxoplasma IgG antibodies yielded Kappa value of 1.0 for cats and mice and 0.79 for seals. These results show that the ELISA-A/G is a suitable method for serological detection of T. gondii infection in multiple host species and has the potential for testing samples from a broad range of domestic, wild, and aquatic mammalian host species. Simultaneous testing of samples from multiple host species on the same ELISA plate, and the use of multiple plates in a single run for large scale screening will enhance the cost effectiveness and speed of the test in the control and management of toxoplasmosis. This study also shows the effectiveness of the protein A/G conjugate in a modified WB assay for confirmation of T. gondii infection in mammalian hosts. Appropriate validation studies using field samples from various host species to validate the performance of ELISA-A/G is recommended prior to its application for diagnostic and surveillance programs.

Visualization of Ubiquitin Conjugates Using Ubiquitin-Mediated Fluorescence Complementation Analysis

Ubiquitin-family peptide conjugation regulates the functions and stabilities of many proteins. Numerous cellular proteins are modified by covalent conjugation of ubiquitin-family peptides to specific lysine residues. These modifications provide a flexible means for regulating the properties of the substrate proteins. Because ubiquitin can be conjugated to substrate proteins at many different sites and in many topological configurations, these modifications have the potential to confer a wide range of functional states to the modified proteins. Ubiquitin conjugation is typically detected by immunoprecipitation of a putative substrate protein followed by immunoblotting to detect ubiquitin conjugated to the substrate. However, this assay cannot be used to detect ubiquitin conjugates in live cells. It is also difficult to determine the subcellular distribution of a specific ubiquitin conjugate using this approach. To visualize ubiquitin conjugates in live cells, we have developed the ubiquitin-mediated fluorescence complementation assay, which is based on the association of fragments of fluorescent proteins when ubiquitin fused to one fragment is conjugated to a substrate protein fused to a complementary fragment. This protocol focuses on the visualization of ubiquitin conjugated in cultured mammalian cells, but it can be adapted to any cell type or aerobically grown organism that can be genetically modified to express the fusion proteins.

New Bifunctional Chelator for 64Cu-Immuno-Positron Emission Tomography

A new tetraazamacrocyclic bifunctional chelator, TE2A-Bn-NCS, was synthesized in high overall yield from cyclam. An extra functional group (NCS) was introduced to the N-atom of TE2A for specific conjugation with antibody. The Cu complex of TE2A-Bn-NCS showed high kinetic stability in acidic decomplexation and cyclic voltammetry studies. X-ray structure determination of the Cu-TE2A-Bn-NH2 complex confirmed octahedral geometry, in which copper atom is strongly coordinated by four macrocyclic nitrogens in equatorial positions and two carboxylate oxygen atoms occupy the elongated axial positions. Trastuzumab was conjugated with TE2A-Bn-NCS and then radiolabeled with 64Cu quantitatively at room temperature within 10 min. Biodistribution studies showed that the 64Cu-labeled TE2A-Bn-NCS-trastuzumab conjugates maintain high stability in physiological conditions, and NIH3T6.7 tumors were clearly visualized up to 3 days by 64Cu-immuno-positron emission tomography imaging in animal models.

SNAP-Tag Technology: A Powerful Tool for Site Specific Conjugation of Therapeutic and Imaging Agents

In the past two decades, immense advances have been achieved in the engineering, production and purifying of recombinant proteins. These proteins are being widely utilized in many fields of biology, biotechnology and medicine, including diagnostic and therapeutic applications. These applications often require the modification or conjugation of these proteins with other molecules. Researchers are spending many efforts to develop and improve the methods of protein modifications. A main challenge they face is derivatizing proteins without affecting their structure and biological function. The conjugation methods available today include random and specific chemical modifications on endogenous amino acids or carbohydrate of the protein of interest. Other methods utilize self-labeling tags as fusion partners to the original protein enabling site-specific conjugation. SNAP-tag is one of the most promising self-labeling tags, which reacts specifically, rapidly and covalently with benzylguanine (BG) derivatives. SNAP-tag fusion proteins have been successfully used for imaging living cells. Recently, several studies have utilized the SNAP technology for generating antibody-based diagnostic and therapeutic tools. We here review these approaches and their possible impact on improving cancer targeting.

Multicellular Computing Using Conjugation for Wiring

Recent efforts in synthetic biology have focussed on the implementation of logical functions within living cells. One aim is to facilitate both internal “re-programming” and external control of cells, with potential applications in a wide range of domains. However, fundamental limitations on the degree to which single cells may be re-engineered have led to a growth of interest in multicellular systems, in which a “computation” is distributed over a number of different cell types, in a manner analogous to modern computer networks. Within this model, individual cell type perform specific sub-tasks, the results of which are then communicated to other cell types for further processing. The manner in which outputs are communicated is therefore of great significance to the overall success of such a scheme. Previous experiments in distributed cellular computation have used global communication schemes, such as quorum sensing (QS), to implement the “wiring” between cell types. While useful, this method lacks specificity, and limits the amount of information that may be transferred at any one time. We propose an alternative scheme, based on specific cell-cell conjugation. This mechanism allows for the direct transfer of genetic information between bacteria, via circular DNA strands known as plasmids. We design a multi-cellular population that is able to compute, in a distributed fashion, a Boolean XOR function. Through this, we describe a general scheme for distributed logic that works by mixing different strains in a single population; this constitutes an important advantage of our novel approach. Importantly, the amount of genetic information exchanged through conjugation is significantly higher than the amount possible through QS-based communication. We provide full computational modelling and simulation results, using deterministic, stochastic and spatially-explicit methods. These simulations explore the behaviour of one possible conjugation-wired cellular computing system under different conditions, and provide baseline information for future laboratory implementations.

Convergence properties of a class of nonlinear conjugate gradient methods

Conjugate gradient methods are a class of important methods for unconstrained optimization problems, especially when the dimension is large. In this paper, we study a class of modified conjugate gradient methods based on the famous LS conjugate gradient method, which produces a sufficient descent direction at each iteration and converges globally provided that the line search satisfies the strong Wolfe condition. At the same time, a new specific nonlinear conjugate gradient method is constructed. Our numerical results show that the new method is very efficient for the given test problems by comparing with the famous LS method, PRP method and CG-DESCENT method.

Murine Typhus in Humans, Yucatan, Mexico

To the Editor: Rickettsia typhi is the causal agent of murine typhus, a febrile illness affecting humans worldwide (1). In Mexico, recent studies demonstrated a 14% prevalence of antibodies against typhus group rickettsiae in healthy adult blood donors in Mexico City, and a recent nonfatal case of endemic typhus was reported in Yucatan (2,3). In May 2011, a 42-year-old woman and her 12-year-old son sought care at the clinical service of the Autonomous University of Yucatan. They had malaise, headache, fever (39°C), fibromyalgia, sore throat, and fatigue and an erythematous rash on the chest that after 6 days spread to the abdomen and extremities. Dengue fever was diagnosed, and the patients were treated empirically with acyclovir, methanesulfonamide, N-(4-nitro-2-phenoxyphenyl) and clarithromycin. Dengue could not be confirmed by laboratory testing. Murine typhus was diagnosed on the basis of PCR amplification and immunofluorescent assay for antibodies to R. typhi. Rickettsia species was determined by sequencing of rickettsial genes. Three serum samples were collected from the woman (8, 12, and 16 days after illness onset) and 1 from the boy (8 days) in 3.8% sodium citrate as anticoagulant, and DNA was extracted immediately by QIAamp DNA Blood Mini Kit (QIAGEN Valencia, CA, USA) in accordance with the manufacturer’s instructions. Single-step PCR amplification was performed by using genus-specific primers for the rickettsial 17-kDa protein and citrate synthase (gltA) genes as reported (4) Sequences of the citrate synthase and 17-kDa PCR products were compared at the National Center for Biotechnology Information BLAST software (5). Three PCR amplicons of both genes were fully sequenced and compared with sequences in GenBank. The 17-kDa and citrate synthase fragment sequences (GenBank accession nos. {type:entrez-nucleotide,attrs:{text:JX198507,term_id:402230109}}JX198507 and {type:entrez-nucleotide,attrs:{text:JX458814,term_id:406654549}}JX458814) showed 99% and 100% identity, respectively, with R. typhi strain Wilmington strain (GenBank accession no. {type:entrez-nucleotide,attrs:{text:AE017197.1,term_id:51459527}}AE017197.1) (Table). Table Ig detection by immunofluorescent assay and molecular results by PCR and sequence identity of the amplicons of gltA and 17-kDa genes of Rickettsia spp. from 2 patients with murine typhus, Yucatan, Mexico Immunofluorescent assay was performed by using R. rickettsii and R. typhi antigen fixed on slides. We examined the serum samples for IgG and IgM, assessing reactivity of γ chain–specific and μ heavy chain–specific secondary conjugates, respectively, with rickettsial antigens. All 3 samples from the woman and the sample from the boy contained antibodies to R. typhi (Table). Both patients were treated with 100 mg of oral doxycycline 2×/day for 7 days (boy), and 10 days (woman); symptoms improved in 72 hours for the child. The woman’s symptoms resolved completely in 5 days. Typhus has been endemic in Mexico since before the conquest period (6). Socioeconomic aspects play a major role in zoonotic diseases, such as rickettsioses, especially in their distribution in urban and suburban areas because of factors such as marginalized communities, animal breeding, education levels, poverty, and social exclusion from health systems. Overcrowding resulting from migration from rural areas to large urban centers contributes to increased zoonoses in urban areas. Also contributing is the ecologic imbalance of flora and fauna associated with deteriorating sanitary conditions in areas where mammals involved in the cycle of R. typhi, such as rodents and opossum, may live in the same habitat as humans and colonize backyards, waste deposit area, and areas around the neighborhoods where they can find food. The concurrence and presence of mammals, vectors, and humans may contribute to maintaining transmission of endemic typhus in a reduced area, with the possibility to cause outbreaks (7,8). Housing conditions and culture, such as courtyards with vegetation and presence of pets, in several suburban areas of Yucatan encourage close contact between humans and possible reservoirs for several infectious diseases, such as mice, rats, opossums, dogs and cats, and their ectoparasites (9). Because housing and cultural conditions are similar in all countries of Latin America, endemic typhus probably is transmitted in the same way: by coexistence with domestic animals and close contact with wild reservoirs. Epidemiologic control should be closely linked to education aimed at encouraging villagers to interrupt the cycle of transmission and thus prevent the disease. We have confirmed the presence of murine typhus in Yucatan. The finding of human cases demonstrates the need to consider R. typhi infection in the differential diagnosis of febrile illnesses considered endemic in Yucatan, such as dengue fever and leptospirosis (10). Early and accurate diagnosis should enable physicians to treat this disease appropriately and early in the clinical course to prevent increased illness and death.

Role ofN- orC-Terminal Biotinylation in Autoantibody Recognition of Citrullin Containing Filaggrin Epitope Peptides in Rheumatoid Arthritis

Here, we report on the synthesis, conformational analysis, and autoantibody binding properties of new sets of rheumatoid arthritis (RA) specific biotin-peptide conjugates derived from filaggrin epitope peptides. The biotin with or without a linker was attached to the Cit or Arg containing epitope core ((311)TXGRS(315)) or epitope region ((306)SHQESTXGXSXGRSGRSGS(324)) peptide (where X = Cit), through an amide bond at the N- or C-terminal of the epitopes. Antibody binding was detected by indirect enzyme-linked immunosorbent assay (ELISA) using sera from RA, Systemic lupus erythematosus (SLE) patients, as well as healthy individuals, and the secondary structure of conjugates was investigated by electronic circular dichroism (ECD). We found that autoantibodies from RA patients recognize specifically both filaggrin epitope region ((306)SHQESTXGXSXGRSGRSGS(324)) and short epitope core ((311)TXGRS(315)) peptides. Our data also indicate that the positioning of the biotin label within a peptide sequence can markedly influence the antibody binding, but the length of the linker incorporated has essentially no effect on the recognition. ECD experiments demonstrate that the Arg/Cit change does not influence the solution conformation of the peptide conjugates. However, the presence and position of the biotin moiety has a pronounced effect on the conformation of the 5-mer epitope core peptides, while it does not alter the secondary structure of the 19-mer epitope region peptides.

High prevalence of VIM-4 and NDM-1 metallo-β-lactamase among carbapenem-resistant Enterobacteriaceae

The purpose of this study was to identify the mechanisms leading to carbapenem resistance among multidrug-resistant Enterobacteriaceae isolates recovered from hospitalized patients with nosocomial infections in Mubarak Al Kabeer Hospital, Kuwait. Fourteen carbapenem-resistant Enterobacteriaceae isolates were obtained from inpatients in different wards and intensive care units between April 2009 and February 2011. Antibiotic susceptibilities were determined using the E-test method. Genes encoding β-lactamases were characterized by specific PCR amplification, sequencing and conjugation assays. All isolates were identified as metallo-β-lactamase (MBL) producers using phenotypic and molecular methods. Eleven of the 14 isolates produced VIM-4 (six Klebsiella pneumoniae, three Escherichia coli, one Enterobacter cloacae and one Klebsiella oxytoca). Three K. pneumoniae isolates produced the MBL NDM-1 and co-produced the plasmid-encoded AmpC CMY-4. The VIM-4-producing isolates co-produced extended-spectrum β-lactamases including CTX-M-15 and some SHV derivatives. The VIM-4 gene was not transferable by conjugation studies of six selected strains. We demonstrated here the emergence of VIM-4- and NDM-1-producing isolates in the largest teaching hospital in Kuwait.

Measuring T cell activation in T cell-APC conjugates using the ImageStream imaging flow cytometer (P5043)

Abstract Adaptive immune responses require antigen presentation to antigen-specific effector cells. Upon interaction between the antigen presenting cell (APC), specific antigen and T cell there is a reorganization of the cytoskeleton and recruitment of adhesive and signaling molecules to the site of intercellular contact forming an immunological synapse (IS). Upon formation of a functional IS, signaling molecules join the clusters and contribute to the signaling cascade leading to translocation of nuclear factors from the cytoplasm to the nucleus culminating in gene activation. Recruitment of these molecules is measured by imaging cell conjugates directly. To analyze a statistically significant number of specific conjugates we used the ImageStream imaging flow cytometer with a 60X objective, which objectively and rapidly collects large numbers of images and provides quantitative image analysis tools to evaluate subcellular localization of molecules. In this study we evaluate the specific location of the adhesion and signaling molecules LFA-1 and Lck within the IS complex in T cells when presented with SEB pulsed APC. In addition we measured the translocation of NFkB in the T cell from the cytoplasm to the nucleus showing the activation of the T cells when conjugated to APC.

Z-band Alternatively Spliced PDZ Motif Protein (ZASP) Is the Major O-Linked β-N-Acetylglucosamine-substituted Protein in Human Heart Myofibrils

We studied O-linked β-N-acetylglucosamine (O-GlcNAc) modification of contractile proteins in human heart using SDS-PAGE and three detection methods: specific enzymatic conjugation of O-GlcNAc with UDP-N-azidoacetylgalactosamine (UDP-GalNAz) that is then linked to a tetramethylrhodamine fluorescent tag and CTD110.6 and RL2 monoclonal antibodies to O-GlcNAc. All three methods showed that O-GlcNAc modification was predominantly in a group of bands ~90 kDa that did not correspond to any of the major myofibrillar proteins. MALDI-MS/MS identified the 90-kDa band as the protein ZASP (Z-band alternatively spliced PDZ motif protein), a minor component of the Z-disc (about 1 per 400 α-actinin) important for myofibrillar development and mechanotransduction. This was confirmed by the co-localization of O-GlcNAc and ZASP in Western blotting and by immunofluorescence microscopy. O-GlcNAcylation of ZASP increased in diseased heart, being 49 ± 5% of all O-GlcNAc in donor, 68 ± 9% in end-stage failing heart, and 76 ± 6% in myectomy muscle samples (donor versus myectomy p < 0.05). ZASP is only 22% of all O-GlcNAcylated proteins in mouse heart myofibrils.

Precision Biopolymers from Protein Precursors for Biomedical Applications

The synthesis of biohybrid materials with tailored functional properties represents a topic of emerging interest. Combining proteins as natural, macromolecular building blocks, and synthetic polymers opens access to giant brush-like biopolymers of high structural definition. The properties of these precision polypeptide copolymers can be tailored through various chemical modifications along their polypeptide backbone, which expands the repertoire of known protein-based materials to address biomedical applications. In this article, the synthetic strategies for the design of precision biopolymers from proteins through amino acid specific conjugation reagents are highlighted and the different functionalization strategies, their characterization, and applications are discussed.

Exploiting furan's versatile reactivity in reversible and irreversible orthogonal peptide labeling

A general method for the facile and versatile decoration of peptides is proposed exploiting furan based cycloaddition and electrophilic aromatic substitution reactions. Given the commercial availability of furylalanine derivatives for peptide synthesis, the current work significantly enlarges the toolbox of available methodologies for site specific labeling and conjugation of peptide probes.