In contrast to the large body of work published on nonelectrolyte and strong electrolyte solutions, theoretical or correlational work is sparse for aqueous, volatile weak electrolytes. Van Krevelen's (1949) studies apply only to ammonia rich systems; further, they are limited to restricted ranges of ammonia/acid ratios and, for some cases, require experimental information which is not available. The more recent work of Edwards et al. (1975) is limited to low concentrations of weak electrolytes and to temperatures below (about) 80°C. The present work extends Edwards' earlier efforts to higher concentrations and higher temperatures.The purpose of this work is to extend a previously presented thermodynamic framework for calculating vaporliquid equilibria for solutions containing volatile weak electrolytes as commonly encountered in the chemical and related industries. The electrolytes examined are ammonia, carbon dioxide, hydrogen sulfide, and sulfur dioxide for the temperature range 0' to 17OOC; the composition range, depending on extent of ionization, may be as high as 10 to 20 moial. Limited information is also given for hydrogen cyanide.Parameters Al, Az, Aa, and A4 are given in Table 1. Parameters for the first and second dissociation constants of carbon dioxide are based on data reported by Clark ( 1966) ; for hydrogen sulfide, ammonia, hydrogen cyanide, and water, the parameters are those given by Tsonopoulos t In some cases it is preferable to write instead of Equation (2) -UNH&P -P w~) RT ~NH.@NE~$ = ~N H , Y O N + J~N H , exp ooo,(P -Pw') yco,@co,P = mco,y*co,Hco, exp RT yielding seventeen simultaneous, independent equations containing tho known partial pressures.

Hepatitis C virus (HCV) is a major cause of chronic liver disease, with an estimated 170 million people infected worldwide. Low yields, poor stability, and inefficient binding to conventional EM grids have posed significant challenges to the purification and structural analysis of HCV. In this report, we generated an infectious HCV genome with an affinity tag fused to the E2 envelope glycoprotein. Using affinity grids, previously described to isolate proteins and macromolecular complexes for single-particle EM, we were able to purify enveloped particles directly from cell culture media. This approach allowed for rapid in situ purification of virions and increased particle density that were instrumental for cryo-EM and cryoelectron tomography (cryo-ET). Moreover, it enabled ultrastructural analysis of virions produced by primary human hepatocytes. HCV appears to be the most structurally irregular member of the Flaviviridae family. Particles are spherical, with spike-like projections, and heterogeneous in size ranging from 40 to 100 nm in diameter. Exosomes, although isolated from unfractionated culture media, were absent in highly infectious, purified virus preparations. Cryo-ET studies provided low-resolution 3D structural information of highly infectious virions. In addition to apolipoprotein (apo)E, HCV particles also incorporate apoB and apoA-I. In general, host apolipoproteins were more readily accessible to antibody labeling than HCV glycoproteins, suggesting either lower abundance or masking by host proteins.enveloped virus | hepacivirus | lipoviral particle | virus structure | virus assembly H epatitis C virus (HCV) is an important human pathogen that infects the liver and establishes chronic infection in the majority of cases, leading to cirrhosis and hepatocellular carcinoma (HCC) over the course of many years. More than 170 million people, ∼3% of the world's population, have been infected with HCV. Each year, 4-5% of patients with HCVinduced cirrhosis develop HCC, making HCV infection the leading indicator for liver transplantation in many areas of the world (1). Surgery, however, does not provide a cure because the donor organ universally becomes reinfected. A prophylactic vaccine is not available and despite the recent addition of HCV-specific protease inhibitors to the pegylated (peg)-IFN and ribavirin regimen, which has increased the cure rate, better therapies are still needed to solve the emergence of resistant variants, severe side effects and suboptimal response rates in cirrhotic patients (2).HCV is a single-stranded, positive-sense RNA virus in the family Flaviviridae. The HCV genome is ∼9.6 kb in length and encodes a long polyprotein of more than 3000 amino acids that is proteolytically processed to generate 10 mature viral proteins. Viral structural proteins are encoded by the first third of the polyprotein and include core or capsid protein (C) and the envelope glycoproteins E1 and E2. p7 (a viroporin) and nonstructural proteins, encoded by the C-terminal two-thirds of the polyprotein, pla...

During dengue virus infection of host cells, intracellular membranes are rearranged into distinct subcellular structures such as double-membrane vesicles, convoluted membranes, and tubular structures. Recent electron tomographic studies have provided a detailed three-dimensional architecture of the double-membrane vesicles, representing the sites of dengue virus replication, but temporal and spatial evidence linking membrane morphogenesis with viral RNA synthesis is lacking. Integrating techniques in electron tomography and molecular virology, we defined an early period in virus-infected mosquito cells during which the formation of a virus-modified membrane structure, the double-membrane vesicle, is proportional to the rate of viral RNA synthesis. Convoluted membranes were absent in dengue virus-infected C6/36 cells. Electron tomographic reconstructions elucidated a high-resolution view of the replication complexes inside vesicles and allowed us to identify distinct pathways of particle formation. Hence, our findings extend the structural details of dengue virus replication within mosquito cells and highlight their differences from mammalian cells. IMPORTANCEDengue virus induces several distinct intracellular membrane structures within the endoplasmic reticulum of mammalian cells. These structures, including double-membrane vesicles and convoluted membranes, are linked, respectively, with viral replication and viral protein processing. However, dengue virus cycles between two disparate animal groups with differing physiologies: mammals and mosquitoes. Using techniques in electron microscopy, we examined the differences between intracellular structures induced by dengue virus in mosquito cells. Additionally, we utilized techniques in molecular virology to temporally link events in virus replication to the formation of these dengue virus-induced membrane structures. Dengue virus (DENV) is a flavivirus, within the Flaviviridae family. There are four distinct serotypes, referred to as DENV-1, -2, -3, and -4. DENV is an enveloped virus with an 11-kb positive-sense RNA genome encoding a polyprotein which is coand posttranslationally processed. Three structural proteins (C, prM, and E) constitute the virus particle, and the seven nonstructural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5) function in viral RNA replication (1). DENV causes one of the most aggressive arthropod-borne viral diseases, with approximately 100 to 350 million cases annually. Of these, approximately 500,000 patients are admitted to hospitals with a more severe form of the disease, referred to as dengue hemorrhagic fever and/or dengue shock syndrome (2).During infection, the DENV RNA is translated into a single polyprotein associated with the endoplasmic reticulum (ER) membrane, and cellular and viral proteases cleave the polyprotein, generating the individual proteins required for subsequent viral RNA synthesis and virion assembly. Following cleavage, the viral proteins remain associated with the ER membrane either on the cytoplas...

OBJECTIVE To clarify the prevalence of disease as determined by age, sex and the degree of haematuria at presentation, and to ascertain the merits of using ultrasonography (US), i.v. urography (IVU) or both when imaging the upper urinary tract, in a prospective cohort of patients attending a protocol‐based haematuria clinic. PATIENTS AND METHODS In a two‐tier protocol, as a part of first‐line investigation, all 4020 patients attending the clinic between October 1998 and August 2003 had US and flexible cystoscopy. Subsequently, IVU was used where indicated following abnormal first‐line tests and in patients with persistent haematuria where no abnormality had been detected. RESULTS In all, 2627 men and 1393 women presented with microscopic (53.2%) or macroscopic haematuria (46.8%). The overall prevalence of malignant disease was 12.1%, but for macroscopic haematuria it was 18.9% and for microscopic haematuria 4.8%. Age and sex also influenced the observed rates of disease. Of the upper tract tumours, 70 were identified after abnormal US, with three cases of transitional cell carcinoma identified on IVU after a normal US. CONCLUSIONS The study provides a rationale for the appropriate investigation of all patients, moderated by the age, sex and degree of haematuria, and the ubiquitous use of US with selective IVU based on age, sex and degree of (and persistence of) haematuria.

During dengue virus replication, an incomplete cleavage of the envelope glycoprotein prM, generates a mixture of mature (prM-less) and prM-containing, immature extracellular particles. In this study, sequential immunoprecipitation and cryoelectron microscopy revealed a third type of extracellular particles, the partially mature particles, as the major prM-containing particles in a dengue serotype 2 virus. Changes in the proportion of viral particles in the pr-M junction mutants exhibiting altered levels of prM cleavage suggest that the partially mature particles may represent an intermediate subpopulation in the virus maturation pathway. These findings are consistent with a model suggesting the progressive mode of prM cleavage.Dengue viruses are enveloped, positive-strand RNA viruses in the genus Flavivirus of the family Flaviviridae (19). The viral genome encodes three structural proteins (C, prM/M, and E) and seven nonstructural proteins (19). Two types of genomecontaining particles, the immature and mature particles, can be distinguished by the differences in size and surface morphology and the presence and cleavage status of the envelope glycoprotein prM (19,20). The immature particles are assembled in the endoplasmic reticulum as spherical "spiky" particles of about 60 nm in diameter (36). Each of the spikes is formed by a noncovalent association of three prM-E heterodimers, with the pr portion of prM on the outermost part of the spike providing the main contact (18,36). During the export, the low-pH environment of the trans-Golgi network induces the rearrangement of prM-E heterodimers into a flattened conformation that allows for an internal cleavage of prM by furin (34). The complete prM cleavage generates the mature particles, which are about 50 nm in diameter and present a smooth surface (17). These infectious particles contain 90 E homodimers arranged in groups of three parallel dimers in the "herringbone" pattern (17). Further complexity of the viral particles was observed in studies of dengue virus and West Nile virus in the form of particles having an intermediate conformation between those of the mature and immature particles (3,24,35).Cleavage of prM is a prerequisite for an acquisition of infectivity, as the pr portion of prM functions as a mechanical barrier to protect the fusion loop in the receptor-binding E glycoprotein from undergoing low pH-mediated fusion (7,18,29). Inhibition of the prM cleavage by mutation of the furin cleavage site, treatment of the infected cells with acidotropic amines, or growth of the virus in furin-deficient cells generates noninfectious particles in the extracellular compartment (7,8,10,25,37). During the replication of dengue virus, cleavage of prM is, however, usually incomplete (1,4,9,11,16,21,25,27,32,33). This reflects an inhibition of cleavage mediated by a highly conserved acidic residue at the P3 cleavage position of the pr-M junction (15). Currently, it is not clear how the prM molecules are collectively cleaved in each viral particle. In the "all-or-none...