Academic literature on the topic 'Thiol-reactive small molecules'

Neurodegenerative diseases (NDDs) often represent disorders of protein folding. Rather than large aggregates, recent evidence suggests that soluble oligomers of misfolded proteins are the most neurotoxic species. Emerging evidence points to small, soluble oligomers of misfolded proteins as the cause of synaptic dysfunction and loss, the major pathological correlate to disease progression in many NDDs including Alzheimer’s disease. The protein quality control machinery of the cell, which includes molecular chaperones as found in the endoplasmic reticulum (ER), the ubiquitin-proteasome system (U

For many applications, peptides should be conjugated to carriers. An important example is the conjugation of peptides to proteins, carbohydrates, or lipids for immunological studies. Further examples are the preparation of peptide affinity media and the conjugation of peptides to suitable coating compounds on surfaces for enzyme-linked immunosorbent assay and plasma resonance. The most important consideration in designing conjugates is that the peptide part of the conjugate must retain its biological activity. This means that the site of activity of the peptide must not be involved in the conjugation reaction. However, the active part of the peptide is often not precisely known, which complicates the design of a proper conjugation strategy. In addition, if the peptide is a fragment of a larger biologically active protein, the small peptide will frequently not adopt the conformation (for instance, a loop structure) of the corresponding sequence in the native protein. This might also abolish desired biological properties, such as the possibility to induce functional antibodies recognizing the native protein. In that case, appropriate artificial conformational restrictions should be introduced into the peptide - if possible. From the numerous conjugation methods available, only a few are described in this chapter. One example concerns the application of the homobifunctional cross-linker glutaraldehyde. Heterobifunctional cross-linking is illustrated by coupling of thiol-containing peptides or carriers to sulphydryl-reactive carriers or peptides, respectively. A general and easy method of conjugating peptides to proteins is to make use of homobifunctional cross-linkers. An example of a homobifunctional cross-linker is glutaraldehyde. This bis-aldehyde reacts with amine groups at neutral or basic pH to yield enamines, which can be reduced optionally to amines with sodium cyanoborohydride. The peptide and the protein react selectively via their N-terminus and/or lysine side chains to give not only a very complex mixture of products—peptide-peptide, peptide-protein, and protein-protein conjugates—but also large constructs containing peptide and protein. Typically, several peptide molecules per protein molecule are coupled. In view of the complex reaction pathway, the batch-to-batch reproducibility of the conjugate is difficult to control. If the peptide contains a lysine in the active part, it is recommended to extend the peptide N- or C-terminally with some additional lysines during synthesis in order to provide more amine groups for conjugation.