Creative Biolabs has established a platform to analyze the secondary and tertiary structure of therapeutic drug candidates, utilizing the ultraviolet and visible absorption spectra, strictly following the ICH Topic Q6b guideline. The higher-order structure of the protein product is evaluated with procedures such as Circular Dichroism (CD), Nuclear Magnetic Resonance (NMR), and other suitable techniques, as appropriate.
Protein secondary structure describes stretches or strands with distinct characteristic local structural conformations, based on hydrogen bonds. The two dominant types of secondary structure are the α-helix and the ß-sheet. The α-helix is a right-handed coiled strand, in which the side-chain of the amino acid sequence extend towards the outside. Hydrogen bonds is responsible for the protein structure stability and are formed between the oxygen of the C=O group of each peptide bond and the hydrogen of the N-H group of the peptide bond four amino acids below it in the helix. The side-chain substituents of the amino acid sequence locate beside the N-H groups. The hydrogen bond in a ß-sheet fit between strands (inter-strand). The sheet conformation constitutes of pairs of strands lying side-by-side. The carbonyl oxygens in one strand interact with the amino hydrogens of the adjacent strand. The two strands can locate either parallel or anti-parallel based on the strand directions (N-terminus to C-terminus). The anti-parallel ß-sheet is more stable than parallel because of the more well-arranged hydrogen bonds. Creative Biolabs provide Circular Dichroism to assess the secondary structure of the biopharmaceutical product.
Tertiary Structure is the overall three-dimensional shape of an entire protein molecule. The protein molecules bend and twist in order to achieve maximum stability or lowest energy state. The three-dimensional structure of a protein seems random and irregular. However, it is formed by different stabilizing forces resulting from interactions between the side-chain groups of the amino acid sequence. Neutral, non-polar amino acids with the hydrophobic side-chains, such as phenylalanine or isoleucine, tend to be buried in the core of the protein molecule and thereby shielding them from the outer aqueous environment. Acidic or basic amino acid side-chains are commonly exposed on the surface of the protein since they are hydrophilic. In addition to hydrophobic interaction, disulfide bridges, hydrogen bonds and Salt bridges also help to stabilize the tertiary structure of a protein. Creative Biolabs provide nuclear magnetic resonance and Circular Dichroism to analyze the tertiary structure of the biopharmaceutical product. All the proteins are characterized in house in 2-3 weeks.