Cellobiohydrolasebased Stationary Phases

Chiral stationary phases based on CBH I can resolve acidic and basic racemates into their enantiomers. Higher enantioselectivity is especially obtained for the separation of ^-blocking agents such as propranolol, oxprenolol and metoprolol. Figure 8 shows a chromatogram of propranolol enantiomers on a CBH I-based column.

CBH I has a structural organization with a terminal, 36 residue-long binding domain connected to the rest of the enzyme (i.e. the core) through a flexible arm. The interconnecting region is rich in serine, threonine and proline residues and is highly glycosylated. The core is enzymatically active. CBH I is enzymatically degraded into two fragments, core

Figure 8 Chromatogram of propranolol enantiomers on a CBH

1-based column. HPLC conditions: column, 5.0 mm i.d. x 250 mm; eluent, sodium-acetate buffer pH 4.7, I = 0.01, containing 0.5%

2-propanol; flow rate, 0.3mLmin~1; detection, 254 nm. (Reproduced with permission from Erlandsson P, Marle I, Hansson L et al. (1990) Immobilized cellulase (CBH I) as a chiral stationary phase for direct resolution of enantiomers. Journal ofthe American Chemical Society 112: 4573.)

Figure 8 Chromatogram of propranolol enantiomers on a CBH

1-based column. HPLC conditions: column, 5.0 mm i.d. x 250 mm; eluent, sodium-acetate buffer pH 4.7, I = 0.01, containing 0.5%

2-propanol; flow rate, 0.3mLmin~1; detection, 254 nm. (Reproduced with permission from Erlandsson P, Marle I, Hansson L et al. (1990) Immobilized cellulase (CBH I) as a chiral stationary phase for direct resolution of enantiomers. Journal ofthe American Chemical Society 112: 4573.)

and binding domain. Each fragment has been shown to contain at least one enantioselective site for prop-ranolol. The dominating enantioselective site for propranolol and other solutes is located on the core, the main part of the enzyme. The three-dimensional structure of the active site of CBH I has been elucidated by X-ray crystallography, and it has been shown that the binding site is a tunnel with the dimensions 0.4x0.7x4nm. There are seven acidic amino acid residues, four tryptophan residues and also, tyrosine, serine, threonine, arginine and histidine lining the tunnel. This gives the prerequisite for obtaining stereo-selective binding of a broad range of chiral solutes.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

Get My Free Ebook


Post a comment