Simulation of pelvic osteotomies applied for DDH treatment in pediatric patients using piglet models.

Background: Developmental dysplasia of the hip (DDH) is a common hip joint pathology seen in the pediatric orthopedist's practice. Pelvic osteotomies are the reliable surgical option for DDH treatment in walking patients, and 3 osteotomies (Salter, Dega and Pemberton) are widely used in patients under 6 years of age. Plastic changes in hinge points occur during iliac fragment movement, after the performed osteotomy.

[A study of aspartyl proteases using intramolecularly quenched fluorogenic peptide substrates].

A series of fluorogenic tetra-, penta-, and hexapeptide substrates of the general structure Abz-X-Phe-Phe-Y-Ded (or -pNa in place of -Ded), where X = Ala, Ala-Ala, or Val-Ala and Y = -, Ala, or Ala-Ala, were proposed. Kinetic parameters of hydrolysis of these substrates by pepsin, cathepsin D, human gastricsin, pig pepsin, calf chymosin, and aspergillopepsin A were determined. The compounds synthesized proved to be effective substrates for aspartyl proteases of diverse origins.

Real-time measurements of dark substrate catalysis.

We have developed a novel procedure to monitor the real-time cleavage of natural unmodified peptides (dark substrates). In the competition-based assay, the initial cleavage rate of a fluorogenic peptide substrate is measured in the presence of a second substrate that is not required to exhibit any optical property change upon cleavage. Using a unique experimental design and steady-state enzyme kinetics for a two-substrate system, we were able to determine both Km and k(cat) values for cleavage of the dark substrate.

Dissection of the pH dependence of inhibitor binding energetics for an aspartic protease: direct measurement of the protonation states of the catalytic aspartic acid residues.

The catalytic activity and inhibitor binding energetics of enzymes are often pH-dependent properties. Aspartic proteases comprise an important class of enzyme targets for structure-based drug design. We have performed a complete thermodynamic study of pepstatin binding to plasmepsin II, an aspartic proteinase found in Plasmodium falciparum, using isothermal titration calorimetry and circular dichroism.

Design of sensitive fluorogenic substrates for human cathepsin D.

Cathepsin D is a lysosomal aspartic proteinase that has been implicated in several pathological processes such as breast cancer and Alzheimer's disease. We designed and synthesized a number of quenched fluorogenic substrates with P2 variations in the series AcEE(EDANS)KPIXFFRLGK(DABCYL)E-NH2, where X=cysteine, methylcysteine, ethylcysteine, tert-butylcysteine, carboxymethylcysteine, methionine, valine or isoleucine. Most of the fluorogenic substrates exhibited greater k(cat)/Km ratios than the best cathepsin D substrates described so far.