The molecular determinants responsible for flavivirus host cell binding and tissue tropism are largely unknown, although domain III of the envelope protein has been implicated in these functions. We examined the solution properties and antagonist activity of Langat virus domain III. Our results suggest that domain III adopts a stably folded structure that can mediate binding of tick-borne flaviviruses but not mosquito-borne flaviviruses to their target cells. Three clusters of phylogenetically conserved residues are identified that may be responsible for the vector-specific antagonist activity of domain III.Flaviviruses (family Flaviviridae, genus Flavivirus) are organized into distinct vector-specific classes and serocomplex-specific subgroups (6), although little is known of the molecular determinants that dictate vector-specific pathogenesis, host cell specificity, and tissue tropism. Both mosquito-borne and tick-borne flaviviruses are responsible for epidemics throughout the developing world and pose serious public health threats in developed countries (7, 9, 10). Vaccines are only available to help control infection by yellow fever, Japanese encephalitis, Central European tick-borne encephalitis (TBE), and louping ill flaviviruses (1,2,16,17). No antiviral therapy is available to treat any flavivirus infection.Flavivirus infection requires attachment and entry into a target cell, mediated by binding of the viral envelope (E) proteins to cell surface receptors. The host cell receptor (or receptors) and the region (or regions) of the E protein responsible for flavivirus attachment are unknown, although heparan sulfate has been suggested as one factor mediating the interaction between dengue 2 virus and its target cells (3). It is unknown whether different cell surface receptors and/or envelope-receptor interactions are responsible for flavivirus pathogenesis, host range, and tissue tropism.The structure of the E protein ectodomain from TBE virus has been determined (13). This ectodomain forms a homodimer, with each dimer subunit organized into three domains, designated I, II, and III. Comparisons of E proteins from wild-type viruses with those of attenuated or escape mutant viruses have identified a number of residues in domain III that may be responsible for receptor recognition (4,8,(12)(13)(14). We examined the solution properties of domain III of the E protein from Langat virus (a tick-borne flavivirus) and the ability of this domain to function as an antagonist for virus infectivity. We demonstrate that recombinant domain III adopts a highly stable folded structure in solution and shows reduced infectivity in tick-borne flaviviruses but not mosquitoborne flaviviruses. This suggests that interactions between the envelope protein and its host cell receptor may be vector specific, although it is likely that other factors also influence fla-* Corresponding author. Mailing address:

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The need to increase food production and improve the quality of our environment has prompted a search for materials to control wind and water erosion. This paper is a review of research and development associated with application, methods, and amounts of mulch types-crop residues, chemical soil stabilizers, and feedlot wastes (manure)-required to control wind erosion. An effective wind erosion control treatment is one that can resist a 38.0 m/s wind as measured at 15.2 m. Mulching has becomes an important practice in modern field production. Mulch paper reduces the application of chemical fertilizer and herbicide, weed control and maintain the land temperature. This article reviews the published research on mulches and discusses the opportunities that they solving the problem in agriculture.

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