Yen-Shan Wei

Correlations among mineral components, progressive calcification process and clinical symptoms of calcific tendonitis

OBJECTIVE To establish the correlations among the mineral components, progressive calcification process and clinical symptoms of calcific tendonitis. METHODS The morphology of the calcified deposits on the shoulders of 28 patients with calcific tendonitis was determined by high-resolution ultrasonography. The calcified deposit from each patient was aspirated and determined by the Fourier transform infrared and Raman microspectroscopies. The curve-fitting program was applied to estimate the chemical component in the calcified deposits of calcific tendonitis. RESULTS The morphology of calcified deposits for 28 patients was classified into four shapes: arc shape (7 patients), fragmented/punctuate shape (4 patients), nodular shape (13 patients) and cystic shape (4 patients). These classified shapes markedly correlated with the pain levels in patients. The infrared spectra of all the calcified deposits for 28 patients were easily classified into three types in the blind study and corresponded to the formative, resting and resorptive phases in the progressive calcification process of calcific tendonitis. With the progressive calcification, the IR wavenumber at 1018 cm(-1) assigned to poorly crystalline, non-stoichiometric apatite for the formative phase was shifted to 1028 cm(-1) for the resting phase and then to 1031 cm(-1) due to matured crystalline stoichiometric apatite for the resorptive phase. The curve-fitted results revealed that calcified deposits in calcific tendonitis were composed of different quantities of A-type and B-type carbonated apatites in the three phases. A significant difference was found in carbonated apatite content among the three phases (P < 0.001). CONCLUSIONS The different quantities of A-type and B-type carbonated apatites determined by vibrational microspectroscopy in calcified deposits were well correlated with those of the four shapes of morphologic classification, with the three phases in the progressive calcification process and with the clinical symptoms of calcific tendonitis.

pH- and thermal-dependent conformational transition of PGAIPG, a repeated hexapeptide sequence from tropoelastin.

The secondary structure of PGAIPG (Pro-Gly-Ala-IIe-Pro-Gly), a repeated hexapeptide of tropoelastin, in buffer solution of different pH was determined by using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. The thermal-dependent structural change of PGAIPG in aqueous solution or in solid state was also examined by thermal FTIR microspectroscopy. The conformation of PGAIPG in aqueous solution exhibited a pH-dependent structural characterization. A predominant peak at 1614 cm(-1) (aggregated beta-sheet) with a shoulder near 1560 cm(-1) (beta-sheet) appeared in pH 5.5-8.5 buffer solutions. A new broad shoulder at 1651 cm(-1) (random coil and/or alpha-helix) with 1614 cm(-1) was observed in the pH 4.5 buffer solution. However, the broad shoulder at 1651 cm(-1) was converted to a maximum peak at 1679 cm(-1) (beta-turn/antiparallel beta-sheet) when the pH shifted from 4.5 to 3.5, but the original pronounced peak at 1614 cm(-1) became a shoulder. Once the pH was lowered to 2.5, the IR spectrum of PGAIPG was dominated by major absorption at 1679 cm(-1) with a minor peak at 1552 cm(-1) (alpha-helix/random coil). The result indicates that the pH was a predominant factor to transform PGAIPG structure from aggregated beta-sheet (pH 8.5) to beta-turn/intermolecular antiparallel beta-sheet (pH 2.5). Moreover, a partial conformation of PGAIPG with minor alpha-helix/random coil structures was also explored in the lower pH buffer solution. There was no thermal-dependent structural change for solid-state PGAIPG. The thermal-induced formation of aggregated beta-sheet for PGAIPG in aqueous solution was found from 28 to 30 degrees C, however, which might be correlated with the formation of an opaque gel that turned from clear solution. The formation of aggregated beta-sheet structure for PGAIPG beyond 30 degrees C might be due to the intermolecular hydrogen bonded interaction between the hydrophobic PGAIPG fragments induced by coacervation.