A pressure-jump EPR system to monitor millisecond conformational exchange rates of spin-labeled proteins.

Site-directed spin labeling electron paramagnetic resonance (SDSL-EPR) using nitroxide spin labels is a well-established technology for mapping site-specific secondary and tertiary structure and for monitoring conformational changes in proteins of any degree of complexity, including membrane proteins, with high sensitivity. SDSL-EPR also provides information on protein dynamics in the time scale of ps-µs using continuous wave lineshape analysis and spin lattice relaxation time methods. However, the functionally important time domain of µs-ms, corresponding to large-scale protein motions, is inaccessible to those methods. To extend SDSL-EPR to the longer time domain, the perturbation method of pressure-jump relaxation is implemented. Here, we describe a complete high-pressure EPR system at Q-band for both static pressure and millisecond-timescale pressure-jump measurements on spin-labeled proteins. The instrument enables pressure jumps both up and down from any holding pressure, ranging from atmospheric pressure to the maximum pressure capacity of the system components (~3500 bar). To demonstrate the utility of the system, we characterize a local folding-unfolding equilibrium of T4 lysozyme. The results illustrate the ability of the system to measure thermodynamic and kinetic parameters of protein conformational exchange on the millisecond timescale.

Characteristics and survival of 750 children diagnosed with a renal tumor in the first seven months of life: A collaborative study by the SIOP/GPOH/SFOP, NWTSG, and UKCCSG Wilms tumor study groups.

BACKGROUND: To review the clinical characteristics and survival of infants diagnosed with a primary renal tumor in the first 7 months of life. PROCEDURE: A retrospective data review of patients registered in five large international protocols (SFOP/GPOH/SIOP9/93-01, UKW3 and NWTSG 4 and 5) spanning 1985-2002. RESULTS: 750 (7.2%) of 10,430 registered patients were diagnosed with a renal tumor before age 213 days. Tumor types were Wilms tumor (WT) 58%; congenital mesoblastic nephroma (CMN) 18%; malignant rhabdoid tumor (MRTK) 8%; clear cell sarcoma (CCSK) 2%; non-Wilms tumor (unspecified) 6%; histology unknown, 9%. CMN predominated among tumors diagnosed in the first month of life (54%) but its relative contribution diminished to <10% of all cases diagnosed after the age of 3 months (P < 0.001). Among 639 cases with specified histology and stage, 9/11 stage IV tumors were MRTK, 37/39 bilateral tumors were WT. In 626 children where surgical approach was specified, 522 had immediate nephrectomy. For all cases, 5 years event-free survival (EFS) was 80% and overall survival (OS) 86%. Five years EFS and OS respectively by tumor type were WT (86%, 93%), CMN (94%, 96%), CCSK (49%, 51%), MRTK (16%, 16%). CONCLUSION: Renal tumors diagnosed in the first 7 months of life generally have an excellent prognosis though histology is an important prognostic factor. In the first 2 months of life the prevalence of CMN is high. The relative occurrence of WT increases rapidly with age thereafter. Bilateral tumors are usually WT. Tumors with metastases at diagnosis are usually MRTK.