Bioinertization of NanoLC/MS/MS Systems by Depleting Metal Ions From the Mobile Phases for Phosphoproteomics

We have successfully developed a bioinertized nanoflow liquid chromatography/tandem mass spectrometry (nanoLC/MS/MS) system for the highly sensitive analysis of phosphopeptides by depleting metal ions from the mobile phase. We found that not only direct contact of phosphopeptides with metal components, but also indirect contact with nanoLC pumps through the mobile phase causes significant losses during the recovery of phosphopeptides. Moreover, electrospray ionization was adversely affected by the mobile phase containing multiple metal ions as well as by the sample solvents contaminated with metal ions used in immobilized metal ion affinity chromatography for phosphopeptide enrichment. To solve these problems, metal ions were depleted by inserting an on-line metal ion removal device containing metal-chelating membranes between the gradient mixer and the autosampler. As a result, the peak areas of the identified phosphopeptides increased an average of 9.9-fold overall and 77-fold for multiply phosphorylated peptides with the insertion of the on-line metal ion removal system. This strategy would be applicable to highly sensitive analysis of other phosphorylated biomolecules by microscale-LC/MS/MS

Pulmonary Tuberculous Scar as a Factor Affecting Detection of Lung Cancer

To evaluate the radiologic influence of tuberculous scar on the detection of lung cancer, the results of radiologic screening were retrospectively analyzed. A total of 308, 565 persons above 40 years old underwent the screening from 1986 to 1988. For screening, 100-mm indirect chest radiographs were interpreted by two physicians, and compared to findings on one-year old films if necessary. The screening detected 175 peripheral lung cancers and 25,238 tuberculous scars. Both diseases were prevalent in the elderly. Twenty-seven of 175 lung cancers coexisted with tuberculous scar. The high incidence of tuberculous scar in the elderly caused the seeming increase in the incidence of coexistence of lung cancer. In 14 of 21 coexistent cases reviewed, lung cancer was identified retrospectively on one-year old radiographs. In six patients, lung cancer was misinterpreted as a part of tuberculous scar, despite comparison to one-year old films. The present study suggests that radiographs showing tuberculous scar should be carefully compared to previous films taken at least two years earlier