[1] We used laser-induced fluorescence to measure concentrations of OH and HO 2 at Rishiri Island, Japan, during September 2003. The average maximum daytime concentrations were 2.7 Â 10 6 cm À3 for OH and 5.9 pptv for HO 2 . The observed concentrations were compared to those predicted by a photochemical box model constrained by ancillary observations. During the daytime, the model overestimated HO 2 levels by an average of 89% and OH levels by an average of 35%. This overestimate of OH was rectified when the model was constrained by observed HO 2 levels, suggesting that loss processes of HO 2 were missing in the model. We calculated the loss rates of HO 2 required to bring the modeled HO 2 levels into agreement with observed levels. We then studied processes that are capable of explaining the loss rates, including halogen chemistry, heterogeneous loss of HO 2 on aerosol surfaces, and the possibility of more rapid HO 2 + RO 2 reactions than expected. In the nighttime, most of the observed hourly averaged OH and 10-min-averaged HO 2 concentrations were statistically significant and fell in the ranges (0.7-5.5) Â 10 5 cm À3 and 0.5-4.9 pptv, respectively. Both HO 2 and OH concentrations showed strong positive correlations with total monoterpene concentrations, strongly suggesting that the radicals were produced via reactions of monoterpenes. The median nighttime modeled-to-observed ratios were 1.29 and 0.56 for HO 2 and OH, respectively. These ratios dropped to 0.49 and 0.29 during the evening of 25 September, possibly related to the presence of unmeasured olefinic species or chemical reactions involving RO 2 that are poorly represented in the model.

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Three independent assay methods were used to investigate the activities of antimicrobial peptides (human and rabbit defensins and protegrin from porcine leukocytes) against Mycobacterium tuberculosis in vitro. M. tuberculosis H37Ra was cultured in the presence of human neutrophil peptide 1, synthetic rabbit neutrophil peptide 1, or porcine protegrin 1 at 37؇C for 6 to 48 h, and antimycobacterial activity was measured by CFU assay. These peptides at a concentration of 50 g/ml showed significant antibacterial effects on M. tuberculosis after 24 and 48 h of incubation (85.9 to 97.5% at 24 h and 91.6 to 99.4% at 48 h). A radiometric method and a radial diffusion assay confirmed these observations. Antibacterial activity against M. tuberculosis was independent of calcium (1.0 mM) or magnesium (1.0 mM) and not inhibited by sodium chloride (100 mM). The optimal pH for antibacterial activity against M. tuberculosis was greater than 4.0. Three clinical isolates of M. tuberculosis were also studied, and these peptides showed 86.3 to 99.0% reduction in CFU of these organisms. Morphological studies using scanning electron microscopy showed that defensins caused lesions on the surface of H37Ra. These observations suggest that antimicrobial peptides such as defensins and protegrins may represent an important component of the host defense mechanism against M. tuberculosis and offer a potential new approach to therapy. Mycobacterium tuberculosis is still a leading cause of worldwide disease morbidity and is responsible for more deaths each year than any other single pathogen (32). In addition, the AIDS epidemic has exacerbated the problem. Interest in tuberculosis has been rekindled by the recent resurgence of cases both in the United States and worldwide. The increasing number of multidrug-resistant M. tuberculosis isolates that can be exceedingly difficult and expensive to treat is of particular concern (17). The combination of the increased frequency of infection due to M. tuberculosis and the increase in multidrugresistant M. tuberculosis isolates in patients with AIDS has raised a great deal of concern across the country. Defensins are endogenous antimicrobial peptides (AMPs) that contain 29 to 35 amino acid residues (27). These peptides were first recognized in rabbit and guinea pig neutrophils and in rabbit alveolar macrophages as ''lysosomal cationic proteins'' with antimicrobial properties (42, 43). Much earlier, calf thymus peptide (7) and lysozyme (34) were shown to inhibit the growth of pathogenic mycobacteria. More than 15 mammalian defensins derived from five species have been purified and sequenced, and human neutrophils were found to contain four defensin peptides (15). Defensins have been shown to possess antifungal (10), antibacterial (13, 16, 37), and antiviral (4) activities in vitro. We have previously demonstrated that the defensins human neutrophil peptide 1 (HNP-1), HNP-2, and HNP-3 have activity against Mycobacterium avium-Mycobacterium intracellulare (33). More recently, we have synthesized rabbit neutr...

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