Affinity methods for purification of DNA sequencing reaction products for mass spectrometric analysis

Time-of-flight mass spectrometry has the potential to replace gel electrophoresis for rapid and accurate analysis of DNA sequencing mixtures. However, impurities in the Sanger sequencing reaction solutions can complicate and degrade the mass spectrometric performance. Therefore, a fast purification procedure is necessary for mass spectrometric analysis. Two affinity methods were tested for the capture of the target fragments: a probe strand, complementary to the primer used to initiate synthesis of the Sanger fragments, is immobilized to a solid support either before or after hybridization so that the impurities are readily separated by filtering and washing the support material. The approaches were tested using mock sequencing mixtures assembled from synthetic DNA strands, to which representative impurities could be added. The results showed that the latter method has better overall yield. The recovered fragments were analyzed by matrix-assisted laser desorption/ionization.

Pathological studies on calcification of the intervertebral discs

Calcified deposits in the intervertebral discs of 35 cadavers microradiographically appeared as linear of flake-like densities composed of calcium pyrophosphate dihydrate (CPPD) crystals and as multiple punctates possibly composed of dicalcium phosphate dihydrate (DCPD) crystals. Calcium deposits were found in 57% of the cadavers by microradiography and 63% by light microscopy, without known metabolic or familial history related to articular chondrocalcinosis. By scanning electron microscopy, CPPD crystals were mainly rod-like, rectangular and cuboid and were about 4 to 10 mu in length while DCPD crystals were prismatic and about 20 to 60 microns in length.