Future Exploration of the Outer Heliosphere and Very Local Interstellar Medium by Interstellar Probe.

A detailed overview of the knowledge gaps in our understanding of the heliospheric interaction with the largely unexplored Very Local Interstellar Medium (VLISM) are provided along with predictions of with the scientific discoveries that await. The new measurements required to make progress in this expanding frontier of space physics are discussed and include in-situ plasma and pick-up ion measurements throughout the heliosheath, direct sampling of the VLISM properties such as elemental and isotopic composition, densities, flows, and temperatures of neutral gas, dust and plasma, and remote energetic neutral atom (ENA) and Lyman-alpha (LYA) imaging from vantage points that can uniquely discern the heliospheric shape and bring new information on the interaction with interstellar hydrogen. The implementation of a pragmatic Interstellar Probe mission with a nominal design life to reach 375 Astronomical Units (au) with likely operation out to 550 au are reported as a result of a 4-year NASA funded mission study.

Serologic evidence for hepatitis E virus infection among patients with undifferentiated acute febrile illness in Kibera, Kenya.

BACKGROUND: Hepatitis E (HEV) is an emerging cause of viral hepatitis mainly transmitted through the fecal-oral route. Residents of the Kibera slum of Nairobi, Kenya are at risk for fecal-orally transmitted infections. OBJECTIVE: To quantify the incidence and prevalence of HEV infection among acute febrile illness (AFI) cases using a population-based infectious disease surveillance network. STUDY DESIGN: Cross-sectional serum samples from AFI case-patients between 2009 and 2012 were matched to the age and gender distribution of the Kibera population and tested by IgM and IgG enzyme immunoassays (EIA) and nucleic acid testing (NAT). Serum from healthy residents was also tested by EIA. RESULTS: Of the 482 AFI serum samples tested, 124 (25.7%) and 182 (37.8%) were IgM and IgG reactive, respectively. On multivariate analysis, IgM reactivity was associated with HIV (RR 1.66, 95%CI 1.07, 2.60; p=0.024) while IgG reactivity was associated with increasing age (p<0.001) and HIV (RR 1.93, 95%CI 1.52, 2.46; p<0.001). AFI case-patients were more likely to be IgM (p=0.002) and IgG (p<0.001) reactive compared to healthy residents. The seroincidence by HEV-specific IgM was 84.0 per 1000 person years, however, all 482 samples were negative by NAT. CONCLUSIONS: Serologic evidence for HEV in Kibera suggests a high burden of infection, but NAT did not confirm HEV viremia. Additional testing is needed to determine whether EIAs are susceptible to false positivity in undifferentiated AFI populations before their widespread use.

Correlation of fresh muscle firmness with sensory characteristics of pork loins destined for a quality focused market.

Production of pork for quality-driven export markets offers economic incentive. Pork processors use subjective firmness as a sorting tool for loins intended for high-quality export. The objectives of this study were to determine 1) durometer efficacy in muscle, 2) if firmness on one portion of the loin is indicative of other locations, 3) if 1 d firmness is related to export quality traits, and 4) if variation in firmness is explained by mechanistic measures. Subjective firmness scores (1 = extremely soft and 5 = extremely firm) were determined by a trained individual 1 d (initial time point) postmortem. Loins (North American Meat Processors number 414 Canadian back; = 154) were wet aged for 28 d at 1.7°C. On d 28, a panel of 4 individuals assigned firmness scores on the ventral side of the loin at the area of the 10th rib, the anterior half, and the posterior half of the loin. Durometer readings were collected at the area of the 10th rib on the dorsal and ventral side of the loin. Spearman correlation coefficients were computed in SAS (version 9.3) to account for nonnormality of categorical data. Subjective firmness measurements at d 28 at the 10th rib and on the anterior portion of the loin were not correlated ( ≥ 0.21) with whole loin durometer readings on the dorsal or ventral portion of the loin or the average of the whole loin values. Subjective firmness (d 28) at the 10th rib accounted for 38.44 ( = 0.620) and 48.30% ( = 0.695) of the variation in firmness at the anterior portion of the loin and the posterior portion of the loin, respectively ( ≤ 0.05). One-day subjective firmness measurements were correlated with 28-d Warner-Bratzler shear force measurements ( = 0.174, = 0.03) but were not significantly correlated with sensory characteristics ( ≥ 0.08). Purge tended to be correlated with 1 d firmness ( = 0.136, = 0.10); however, drip and cooking loss, 24-h and 28-d pH, and soluble and insoluble collagen content were not correlated ( ≥ 0.34). Firmness measurements collected in the production facility (1 d) were negatively correlated with iodine value (IV; = -0.199, = 0.02), yet no 28-d subjective firmness measurements were correlated with IV ( ≥ 0.33). When loins not achieving export standards are removed from the population, 1 d firmness was not correlated to export quality or sensory characteristics (d 28). Differences in firmness were not explained by mechanistic measures. Inconsistencies among subjective and objective firmness measurements suggest that the durometer may not be an appropriate way to determine firmness.

Large outbreak of Legionnaires' disease and Pontiac fever at a military base.

We investigated a mixed outbreak of Legionnaires' disease (LD) and Pontiac fever (PF) at a military base to identify the outbreak's environmental source as well as known legionellosis risk factors. Base workers with possible legionellosis were interviewed and, if consenting, underwent testing for legionellosis. A retrospective cohort study collected information on occupants of the buildings closest to the outbreak source. We identified 29 confirmed and probable LD and 38 PF cases. All cases were exposed to airborne pathogens from a cooling tower. Occupants of the building closest to the cooling tower were 6·9 [95% confidence interval (CI) 2·2-22·0] and 5·5 (95% CI 2·1-14·5) times more likely to develop LD and PF, respectively, than occupants of the next closest building. Thorough preventive measures and aggressive responses to outbreaks, including searching for PF cases in mixed legionellosis outbreaks, are essential for legionellosis control.

Inhibition of protein kinase C (PKC) response of voltage-gated calcium (Cav)2.2 channels expressed in Xenopus oocytes by Cavß subunits.

Cav2.2 channels are a substrate for phosphorylation by protein kinase C (PKC) isozymes. The contribution of Cavß, an auxiliary subunit of these channels, in the PKC modulation was studied. Cav2.2 channels were expressed in Xenopus oocytes in various subunit combinations with or without Cavß subunits. Currents were recorded using a two-electrode voltage clamp with barium as the charge carrier (IBa). Acetyl-ß-methylcholine (MCh), an activator of PKCα, potentiated Cav2.2 currents expressed with Cav2.2α1 alone or Cav2.2α1α2/δ. Similarly PKC isozymes α, ßII or ɛ potentiated IBa through Cav2.2α1 subunit channels. In contrast, MCh failed to potentiate currents expressed with Cav2.2α1 and Cavß1b, ß2a, ß3 or ß4 subunits. Similarly, in the presence of Cavß1b subunits, PKC isozymes failed to potentiate these currents; contrarily, PKCs α or ßII decreased the IBa. MCh failed to potentiate Cav2.2α1 subunit currents in the serine/threonine (Ser/Thr)→alanine mutants, T422A, S1757A or S2132A of Cav2.2α1 subunits. Hence Thr-422, Ser-1757 and Ser-2132 may be PKCα isozyme target sites. The action of PKC on these sites was further substantiated by the increased basal IBa along with the loss of MCh potentiation when Ser/Thr was mutated to aspartate. The observation that MCh or PKC isozymes failed to affect Cav2.2 currents in the presence of Cavß subunits suggests that these subunits may have interfered with the interaction between PKC and Ser/Thr sites of Cav2.2α1 subunits. In addition to affecting channel expression and current kinetics, Cavß subunits may also modulate the response of these channels to neurochemicals.

Beat note stabilization of mode-locked lasers for quantum information processing.

We stabilize a chosen radio frequency beat note between two optical fields derived from the same mode-locked laser pulse train in order to coherently manipulate quantum information. This scheme does not require access or active stabilization of the laser repetition rate. We implement and characterize this external lock, in the context of two-photon stimulated Raman transitions between the hyperfine ground states of trapped 171Yb(+) quantum bits.

Eight years of Legionnaires' disease transmission in travellers to a condominium complex in Las Vegas, Nevada.

Travel is a risk factor for Legionnaires' disease. In 2008, two cases were reported in condominium guests where we investigated a 2001 outbreak. We reinvestigated to identify additional cases and determine whether ongoing transmission resulted from persistent colonization of potable water. Exposures were assessed by matched case-control analyses (2001) and case-series interviews (2008). We sampled potable water and other water sources. Isolates were compared using sequence-based typing. From 2001 to 2008, 35 cases were identified. Confirmed cases reported after the cluster in 2001-2002 were initially considered sporadic, but retrospective case-finding identified five additional cases. Cases were more likely than controls to stay in tower 2 of the condominium [matched odds ratio (mOR) 6·1, 95% confidence interval (CI) 1·6-22·9]; transmission was associated with showering duration (mOR 23·0, 95% CI 1·4-384). We characterized a clinical isolate as sequence type 35 (ST35) and detected ST35 in samples of tower 2's potable water in 2001, 2002, and 2008. This prolonged outbreak illustrates the importance of striving for permanent Legionella eradication from potable water.

The impact of feeding diets of high or low energy concentration on carcass measurements and the weight of primal and subprimal lean cuts.

Pigs from four sire lines were allocated to a series of low energy (LE, 3.15 to 3.21 Mcal ME/kg) corn-soybean meal-based diets with 16% wheat midds or high energy diets (HE, 3.41 to 3.45 Mcal ME/kg) with 4.5 to 4.95% choice white grease. All diets contained 6% DDGS. The HE and LE diets of each of the four phases were formulated to have equal lysine:Mcal ME ratios. Barrows (N = 2,178) and gilts (N = 2,274) were fed either high energy (HE) or low energy (LE) diets from 27 kg BW to target BWs of 118, 127, 131.5 and 140.6 kg. Carcass primal and subprimal cut weights were collected. The cut weights and carcass measurements were fitted to allometric functions (Y = A CW(B)) of carcass weight. The significance of diet, sex or sire line with A and B was evaluated by linearizing the equations by log to log transformation. The effect of diet on A and B did not interact with sex or sire line. Thus, the final model was (B)) where Diet = -0.5 for the LE and 0.5 for HE diets and A and B are sire line-sex specific parameters. cut weight = (1+bD(Diet)) A(CW Diet had no affect on loin, Boston butt, picnic, baby back rib, or sparerib weights (p>0.10, bD = -0.003, -0.0029, 0.0002, 0.0047, -0.0025, respectively). Diet affected ham weight (bD = -0.0046, p = 0.01), belly weight (bD = 0.0188, p = 0.001) three-muscle ham weight (bD = -0.014, p = 0.001), boneless loin weight (bD = -0.010, p = 0.001), tenderloin weight (bD = -0.023, p = 0.001), sirloin weight (bD = -0.009, p = 0.034), and fat-free lean mass (bD = -0.0145, p = 0.001). Overall, feeding the LE diets had little impact on primal cut weight except to decrease belly weight. Feeding LE diets increased the weight of lean trimmed cuts by 1 to 2 percent at the same carcass weight.

Incidence of respiratory pathogens in persons hospitalized with pneumonia in two provinces in Thailand.

Although pneumonia is a leading cause of death from infectious disease worldwide, comprehensive information about its causes and incidence in low- and middle-income countries is lacking. Active surveillance of hospitalized patients with pneumonia is ongoing in Thailand. Consenting patients are tested for seven bacterial and 14 viral respiratory pathogens by PCR and viral culture on nasopharyngeal swab specimens, serology on acute/convalescent sera, sputum smears and antigen detection tests on urine. Between September 2003 and December 2005, there were 1730 episodes of radiographically confirmed pneumonia (34·6% in children aged <5 years); 66 patients (3·8%) died. A recognized pathogen was identified in 42·5% of episodes. Respiratory syncytial virus (RSV) infection was associated with 16·7% of all pneumonias, 41·2% in children. The viral pathogen with the highest incidence in children aged <5 years was RSV (417·1/100,000 per year) and in persons aged ≥50 years, influenza virus A (38·8/100,000 per year). These data can help guide health policy towards effective prevention strategies.

Dual detection of Legionella pneumophila and Legionella species by real-time PCR targeting the 23S-5S rRNA gene spacer region.

Although the majority of cases of Legionnaires' disease (LD) are caused by Legionella pneumophila, an increasing number of other Legionella species have been reported to cause human disease. There are no clinical presentations unique to LD and hence accurate laboratory tests are required for early diagnosis. Therefore, we designed a real-time PCR assay that targets the 23S-5S rRNA intergenic spacer region (23S-5S PCR) and allows for detection of all Legionella species and discrimination of L. pneumophila from other Legionella species. In total, 271 isolates representing 50 Legionella species were tested and the assay was validated using 39 culture-positive and 110 culture-negative patient specimens collected between 1989 and 2006. PCR-positive results were obtained with all 39 culture-positive samples (100% sensitivity). Specimens that tested positive according to 23S-5S PCR, but were culture-negative, were further analysed by DNA sequencing of the amplicon or the macrophage infectivity potentiator (mip) gene. In addition to L. pneumophila, Legionella longbeachae, Legionella cincinnatiensis and Legionella micdadei were identified in the specimens. The assay showed a 7-log dynamic range displaying a sensitivity of 7.5 CFU/mL or three genome equivalents per reaction. Sixty-one specimens containing viruses or bacteria other than Legionellae were negative according to 23S-5S PCR, demonstrating its specificity. Use of this assay should contribute to the earlier detection of respiratory disease caused by Legionella species, as well as to increased rates of detection.

Brain MRI, apoliprotein E genotype, and plasma homocysteine in American Indian Alzheimer disease patients and Indian controls.

We obtained brain MRIs, plasma homocysteine levels and apolipoprotein E genotyping for 11 American Indian Alzheimer disease (AD) subjects and 10 Indian controls. We calculated white matter hyperintensity volume (WMHV), whole brain volume (WBV), and ratio of white matter hyperintensity volume to whole brain volume (WMHV/WBV). There were no significant differences between AD subjects and controls in gender, history of hypertension, diabetes, or history of high cholesterol, but hypertension and diabetes were more common among AD subjects. There was no difference between AD and control groups in age (range for all subjects was 61-89 years), % Indian heritage, waist size or body mass index. Median Indian heritage was 50% or greater in both groups. Range of education was 5-13 years in the AD group and 12-16 years in controls. Median plasma homocysteine concentration was higher in AD subjects (11 micromol/L vs. 9.8 micromol/L), but did not achieve statistical significance. Significantly more AD subjects had apolipoprotein Eepsilon4 alleles than did controls (63% vs.10%). Neuroimaging findings were not significantly different between the 2 groups, but AD subjects had greater WMHV (median 15.64 vs. 5.52 cc) and greater WMHV/WBV ratio (median 1.63 vs. 0.65 %) and a far greater range of WMHV. In combined AD subjects and controls, WBV correlated with BMI and age. WMHV and WMHV/WBV correlated inversely with MMSE scores (p = 0.001, 0.002, respectively). In addition, WMHV correlated positively with % Indian heritage (p = 0.047).

Increased rainfall is associated with increased risk for legionellosis.

Legionnaires' disease (LD) is caused by Legionella species, most of which live in water. The Mid-Atlantic region experienced a sharp rise in LD in 2003 coinciding with a period of record-breaking rainfall. To investigate a possible relationship, we analysed the association between monthly legionellosis incidence and monthly rainfall totals from January 1990 to December 2003 in five Mid-Atlantic states. Using negative binomial model a 1-cm increase in rainfall was associated with a 2.6% (RR 1.026, 95% CI 1.012-1.040) increase in legionellosis incidence. The average monthly rainfall from May to September 1990-2002 was 10.4 cm compared to 15.7 cm from May to September 2003. This change in rainfall corresponds to an increased risk for legionellosis of approximately 14.6% (RR 1.146, 95% CI 1.067-1.231). Legionellosis incidence increased during periods of increased rainfall; identification of mechanisms that increase exposure and transmission of Legionella during rainfall might lead to opportunities for prevention.

Legionella pneumophila associated with the protozoan Hartmannella vermiformis in a model multi-species biofilm has reduced susceptibility to disinfectants.

Legionella pneumophila will infect biofilm-associated protozoa, and in this way might be protected from disinfectants in potable water systems. A base biofilm containing Pseudomonas aeruginosa, Klebsiella pneumoniae, and Flavobacterium spp. was grown on steel coupons in potable water prior to the addition of L. pneumophila and the protozoan H. vermiformis. After 7 d, coupons were removed and treated with 0.5 mgl(-1) free residual chlorine (FRC) or 0.5 mgl(-1) monochloramine (MCA) for 15, 60, or 180 min or 24 h. In a second experiment, only L. pneumophila and the base biofilm organisms were present but with an identical treatment protocol. Treatment of L. pneumophila for 180 min in a system without H. vermiformis resulted in log reductions of 2.07 and 2.11 for FRC and MCA, respectively. When H. vermiformis was present, however, the treatment resulted in log reductions of 0.67 and 0.81 for FRC and MCA, respectively. A similar pattern was observed for 15 and 60 min contact times. These results indicate that L. pneumophila was less susceptible to MCA or FRC when associated with biofilm-associated H. vermiformis in a model potable water biofilm.

The effect of pig genetics on palatability, color and physical characteristics of fresh pork loin chops.

The objective of this study was to characterize the quality attributes of pork derived from pigs of the following backgrounds: Duroc, Pietrain (Halothane negative, NN), Pietrain (Halothane positive, nn), Berkshire, Hampshire (rn+), Hampshire (RN-), and a synthetic line. A 10-member panel was trained to evaluate visual appearance of uncooked lean and fat, and flavor and texture of cooked chops. Hunter L*, a*, and b* values, hue angle, cookloss and Warner-Bratzler shear force were also determined. Visual color differences occurred due to genetic background. Chops from Duroc, Berkshire, Pietrain-nn, and the synthetic line were least pink. Chops from Berkshire carcasses appeared to have the most marbling in the lean and those from Pietrain-nn pigs appeared to have the least. Chops from Pietrain-nn and Hampshire-rn+ carcasses had the highest a* values while chops from Duroc, Pietrain-NN, and Hampshire-RN- carcasses had the lowest. Cook loss from chops from Duroc carcasses was lower than that from Hampshire rn+, Pietrain-NN and synthetic line carcasses. Shear force was highest for chops from Pietrain-nn and Hampshire-rn+ carcasses. Chops from Hampshire-RN- carcasses were most juicy followed by those from Hampshire-rn+, Pietrain-NN, Berkshire and Duroc carcasses. Shear force was positively correlated with abnormal flavor intensity, metallic taste, and chewiness (r=0.72, 0.94, and 0.69, respectively), and negatively correlated with sweetness (r=-0.73). Overall, genetic background had significant effects on many of the quality characteristics evaluated.

Role of biofilms in the survival of Legionella pneumophila in a model potable-water system.

Legionellae can infect and multiply intracellularly in both human phagocytic cells and protozoa. Growth of legionellae in the absence of protozoa has been documented only on complex laboratory media. The hypothesis upon which this study was based was that biofilm matrices, known to provide a habitat and a gradient of nutrients, might allow the survival and multiplication of legionellae outside a host cell. This study determined whether Legionella pneumophila can colonize and grow in biofilms with and without an association with Hartmannella vermiformis. The laboratory model used a rotating disc reactor at a retention time of 6.7 h to grow biofilms on stainless steel coupons. The biofilm was composed of Pseudomonas aeruginosa, Klebsiella pneumoniae and a Flavobacterium sp. The levels of L. pneumophila cells present in the biofilm were monitored for 15 d, with and without the presence of H. vermiformis, and it was found that, although unable to replicate in the absence of H. vermiformis, L. pneumophila was able to persist.

Pontiac fever due to Legionella micdadei from a whirlpool spa: possible role of bacterial endotoxin.

During January 1998, a cluster of illnesses occurred among hotel guests in Wisconsin. Ill persons had been exposed to the hotel's whirlpool spa and swimming pool. Symptoms included headache, fever, chills, myalgia, shortness of breath, and fatigue. A diagnosis of Pontiac fever was made, based on serologic evidence of acute infection with Legionella micdadei. High concentrations of heterotrophic bacteria were recovered from the spa, despite apparently high disinfectant levels. L. micdadei was isolated from the swimming pool filter and water from the spa after heat enrichment but not from pools and spas at nearby hotels. Water from hotel pools and spas was tested to determine endotoxin levels; water from the spa of the implicated hotel contained the highest concentration of endotoxin (14,400 endotoxin units/mL). Additional studies are needed to determine the role of endotoxin from legionellae or other bacteria in the pathogenesis of Pontiac fever.

Standardizing Chlamydia pneumoniae assays: recommendations from the Centers for Disease Control and Prevention (USA) and the Laboratory Centre for Disease Control (Canada).

Chlamydia pneumoniae has been associated with atherosclerosis and several other chronic diseases, but reports from different laboratories are highly variable and "gold standards" are lacking, which has led to calls for more standardized approaches to diagnostic testing. Using leading researchers in the field, we reviewed the available approaches to serological testing, culture, DNA amplification, and tissue diagnostics to make specific recommendations. With regard to serological testing, only use of microimmunofluorescence is recommended, standardized definitions for "acute infection" and "past exposure" are proposed, and the use of single immunoglobulin (Ig) G titers for determining acute infection and IgA for determining chronic infection are discouraged. Confirmation of a positive culture result requires propagation of the isolate or confirmation by use of polymerase chain reaction (PCR). Four of 18 PCR assays described in published reports met the proposed validation criteria. More consistent use of control antibodies and tissues and improvement in skill at identifying staining artifacts are necessary to avoid false-positive results of immunohistochemical staining. These standards should be applied in future investigations and periodically modified as indicated.

Legionella drozanskii sp. nov., Legionella rowbothamii sp. nov. and Legionella fallonii sp. nov.: three unusual new Legionella species.

Seven strains of Legionella-like amoebal pathogens (LLAPs) were characterized on the basis of their cultural and staining characteristics, biochemical reactions, serology, cellular fatty acids (CFAs), isoprenoid quinone composition, total DNA relatedness, analysis of 16S rRNA and macrophage infectivity potentiator (mip) gene sequence analyses. All seven strains exhibited limited growth on buffered charcoal yeast extract alpha (BCYE) agar, required cysteine for growth and contained branched-chain CFAs and quinones typical of Legionella species. The bacilli were Gram-negative and catalase-positive. There were varying degrees of serological cross-reactions between these LLAP strains and other previously described Legionella species. Results from the various tests revealed that four LLAP strains represent three unusual new species of Legionella: Legionella drozanskii sp. nov., type strain LLAP-1T; Legionella rowbothamii sp. nov., type strain LLAP-6T; and Legionella fallonii sp. nov., type strain LLAP-10T. Three other LLAP strains, designated LLAP-7FL, LLAP-7NF and LLAP-9, were shown to be members of the species Legionella lytica. The deductions made from the phenetic characteristics of these bacteria were consistent with the phylogenetic relationships inferred from 16S rRNA and mip gene sequence analyses. This study is the first to speciate LLAP strains on the basis of data including quantitative DNA hybridization.

Estimation of the hydrophobic effect in an antigen-antibody protein-protein interface.

Antigen-antibody complexes provide useful models for analyzing the thermodynamics of protein-protein association reactions. We have employed site-directed mutagenesis, X-ray crystallography, and isothermal titration calorimetry to investigate the role of hydrophobic interactions in stabilizing the complex between the Fv fragment of the anti-hen egg white lysozyme (HEL) antibody D1.3 and HEL. Crystal structures of six FvD1.3-HEL mutant complexes in which an interface tryptophan residue (V(L)W92) has been replaced by residues with smaller side chains (alanine, serine, valine, aspartate, histidine, and phenylalanine) were determined to resolutions between 1.75 and 2.00 A. In the wild-type complex, V(L)W92 occupies a large hydrophobic pocket on the surface of HEL and constitutes an energetic "hot spot" for antigen binding. The losses in apolar buried surface area in the mutant complexes, relative to wild-type, range from 25 (V(L)F92) to 115 A(2) (V(L)A92), with no significant shifts in the positions of protein atoms at the mutation site for any of the complexes except V(L)A92, where there is a peptide flip. The affinities of the mutant Fv fragments for HEL are 10-100-fold lower than that of the original antibody. Formation of all six mutant complexes is marked by a decrease in binding enthalpy that exceeds the decrease in binding free energy, such that the loss in enthalpy is partly offset by a compensating gain in entropy. No correlation was observed between decreases in apolar, polar, or aggregate (sum of the apolar and polar) buried surface area in the V(L)92 mutant series and changes in the enthalpy of formation. Conversely, there exist linear correlations between losses of apolar buried surface and decreases in binding free energy (R(2) = 0.937) as well as increases in the solvent portion of the entropy of binding (R(2) = 0.909). The correlation between binding free energy and apolar buried surface area corresponds to 21 cal mol(-1) A(-2) (1 cal = 4.185 J) for the effective hydrophobicity at the V(L)92 mutation site. Furthermore, the slope of the line defined by the correlation between changes in binding free energy and solvent entropy approaches unity, demonstrating that the exclusion of solvent from the binding interface is the predominant energetic factor in the formation of this protein complex. Our estimate of the hydrophobic contribution to binding at site V(L)92 in the D1.3-HEL interface is consistent with values for the hydrophobic effect derived from classical hydrocarbon solubility models. We also show how residue V(L)W92 can contribute significantly less to stabilization when buried in a more polar pocket, illustrating the dependence of the hydrophobic effect on local environment at different sites in a protein-protein interface.