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The 20 standard amino acids are distinguished by their side chains (R groups), which determine protein structure, functi...

Essential amino acids cannot be synthesized by humans and must be obtained from the diet. These nine amino acids have co...

Chirality in amino acids arises from the tetrahedral α-carbon bearing four different substituents. All proteinogenic ami...

Proline analogs like hydroxyproline, fluoroprolines, and azetidine carboxylic acids modify backbone geometry, cis/trans ...

The peptide bond exhibits resonance between a neutral form (C=O, C-N) and a zwitterionic form (C-O⁻, C=N⁺). This delocal...

Cis-trans isomerization in proline is a unique phenomenon arising from the cyclic nature of the pyrrolidine side chain. ...

The Polyproline II (PPII) helix is a left-handed, extended secondary structure (n=3 residues/turn, rise ≈ 3.1 Å) defined...

Peptide bond hydrolysis is a nucleophilic acyl substitution reaction where water attacks the carbonyl carbon, cleaving t...

The Ramachandran plot maps the allowed backbone conformations of proteins by plotting the φ (phi) and ψ (psi) dihedral a...

Hydrogen bonds between backbone amide groups (N-H···O=C) are the defining interactions that stabilize protein secondary ...

Protein folding is driven by the minimization of Gibbs free energy (ΔG), where the native state represents the global th...

Protein folding is driven by the thermodynamic necessity to minimize free energy, a process conceptualized as the foldin...

Molecular chaperones ensure proteins achieve their functional 3D conformations without aggregating. Key systems include ...

Co-translational folding describes the process where a nascent polypeptide begins acquiring its 3D structure while still...

The ribosomal exit tunnel is a 100Å channel through which nascent polypeptides emerge. Its geometry permits α-helix form...

The molten globule is a compact folding intermediate with native-like secondary structure but a fluid, dynamic tertiary ...

CMA is a selective autophagy pathway where cytosolic proteins containing KFERQ-like motifs are recognized by Hsc70, deli...

Protein misfolding occurs when a polypeptide chain fails to adopt its functional native 3D conformation. Misfolded prote...

The kinetics of aggregation typically follow a sigmoidal curve characterized by a rate-limiting lag phase (primary nucle...

Amyloid fibril formation follows nucleation-dependent polymerization kinetics characterized by a sigmoidal time course. ...

Amyloidogenesis is the process by which proteins assemble into ordered, insoluble fibrils with a cross-β structure. Prio...

Therapeutic strategies for protein aggregation diseases increasingly target specific microscopic kinetic steps: native s...

Pin1 is a unique peptidyl-prolyl isomerase that regulates protein conformation by catalyzing cis-trans isomerization of ...

Ribosomopathies are diseases caused by defects in ribosome biogenesis or function, manifesting with tissue-specific phen...

Ribosomal translation synthesizes proteins by decoding mRNA into polypeptide chains through initiation, elongation, and ...

NRPS is a microbial enzymatic system that constructs complex peptides without mRNA templates or ribosomes. Modular megas...

Aminoacyl-tRNA synthetases (aaRS) are essential enzymes that charge tRNA molecules with their cognate amino acids. This ...

Co-translational folding describes the process where a nascent polypeptide begins acquiring its 3D structure while still...

Solid-phase peptide synthesis (SPPS) is a chemical method for constructing peptides by sequentially adding protected ami...

Post-translational modifications are covalent alterations to proteins following biosynthesis, exponentially expanding th...

Intrinsically Disordered Proteins (IDPs) are hotspots for post-translational modifications due to their accessible, exte...

Co-translational Post-Translational Modifications (PTMs) are chemical alterations enacted on a nascent polypeptide chain...

The ubiquitin-proteasome system (UPS) is the major pathway for regulated protein degradation in eukaryotes. Proteins are...

IDPs challenge the traditional structure-function paradigm by existing as dynamic conformational ensembles. Their disord...

SLiMs are compact, degenerate amino acid sequences (3-10 residues) that mediate transient protein-protein interactions. ...

Inteins are autocatalytic protein domains that excise themselves from precursor polypeptides while ligating the flanking...

Liquid-liquid phase separation (LLPS) is the process by which proteins and nucleic acids demix from the cytoplasm to for...

Quaternary structure describes the assembly of multiple polypeptide subunits into functional protein complexes. Alloster...

Mass spectrometry-based proteomics enables large-scale identification and quantification of proteins using ESI and MALDI...

Combinatorial biosynthesis involves the genetic engineering of Non-Ribosomal Peptide Synthetases (NRPS), modular enzymes...

Siderophores are high-affinity iron-chelating compounds secreted by microorganisms to solubilize and transport ferric ir...

RiPPs represent a diverse superfamily of natural products that are biosynthesized through ribosomal translation of a pre...

PKS-NRPS hybrid systems combine polyketide synthase and non-ribosomal peptide synthetase modules to produce structurally...