Tests of hypotheses on the adaptive value of an extended male phase in the hermaphroditic shrimp Lysmata wurdemanni (Caridea: Hippolytidae)

Hypotheses on delayed sex change in the protandric simultaneous hermaphrodite Lysmata wurdemanni were tested with observations from population samples, mating experiments, and experiments on sex change under optimal and suboptimal breeding conditions. Male-phase individuals (MPs) much larger than the minimum size of sex change were most frequent in a natural population from fall through early spring. The hypothesis was tested that some MPs delay sex change to the simultaneous hermaphrodite female-phase (FP) because MPs are more competitive in obtaining copulations with parturial FPs than are FPs mating as males (MFPs). In different experiments, parturial FPs were maintained with two potential male mating partners (large MP and MFP, small MP and MFP, large MP and small MP) through the parturial molt and spawning; activities were recorded with time-lapse video. MFPs gained the single copulation with the parturial FP as frequently as MPs, large or small, but large MPs copulated with more FPs than small MPs. The hypothesis of FP reversion to large MP was tested experimentally and rejected. Rate of change of MP to FP was much lower in large MPs maintained under suboptimal (fall/winter) than optimal (spring/summer) breeding conditions. The results presented here suggest that the occurrence of large MPs from the fall to early spring is better explained by abiotic proximate factors related to breeding than by socially mediated sex change in different demographic environments.     

The minimal fusion peptide of simian immunodeficiency virus corresponds to the 11 first residues of gp32.

We had previously predicted successfully the minimal fusion peptides (FPs) of the human immunodeficiency virus 1 (HIV-1) gp41 and the bovine leukemia virus (BLV) gp30 using an original approach based on the obliquity/fusogenicity relationship of tilted peptides. In this paper, we have used the same method to predict the shortest FP capable of inducing optimal fusion in vitro of the simian immunodeficiency virus (SIV) mac isolate and of other SIVs and human immunodeficiency virus (HIV-2) isolates. In each case, the 11-residue-long peptide was predicted as the minimal FP. For the SIV mac isolate, liposome lipid-mixing and leakage assays confirmed that this peptide is the shortest peptide inducing optimal fusion in vitro, being therefore the minimal FP. These results are another piece of evidence that the tilted properties of FPs are important for the fusion process and that our method can be used to predict the minimal FPs of other viruses.     

Multicolor Whole-Cell Bacterial Sensing Using a Synchronous Fluorescence Spectroscopy-Based Approach

The wide collection of currently available fluorescent proteins (FPs) offers new possibilities for multicolor reporter gene-based studies of bacterial functions. However, the simultaneous use of multiple FPs is often limited by the bleed-through of their emission spectra. Here we introduce an original approach for detection and separation of multiple overlapping fluorescent signals from mixtures of bioreporters strains. The proposed method relies on the coupling of synchronous fluorescent spectroscopy (SFS) with blind spectral decomposition achieved by the Canonical Polyadic (CP) decomposition (also known as Candecomp/Parafac) of three-dimensional data arrays. Due to the substantial narrowing of FP emission spectra and sensitive detection of multiple FPs in a one-step scan, SFS reduced spectral overlap and improved the selectivity of the CP unmixing procedure. When tested on mixtures of labeled E. coli strains, the SFS/CP approach could easily extract the contribution of at least four overlapping FPs. Furthermore, it allowed to simultaneously monitor the expression of three iron responsive genes and pyoverdine production in P. aeruginosa. Implemented in a convenient microplate format, this multiplex fluorescent reporter method provides a useful tool to study complex processes with different variables in bacterial systems.     

Acoustic feature selection and classification of emotions in speech using a 3D continuous emotion model

In this paper we report the results obtained from experiments with a database of emotional speech in English in order to find the most important acoustic features to estimate Emotion Primitives which determine the emotional content on speech. We are interested in exploiting the potential benefits of continuous emotion models, so in this paper we demonstrate the feasibility of applying this approach to annotation of emotional speech and we explore ways to take advantage of this kind of annotation to improve the automatic classification of basic emotions.     

An evaluation, comparison, and accurate benchmarking of several publicly available MS/MS search algorithms: sensitivity and specificity analysis

MS/MS and associated database search algorithms are essential proteomic tools for identifying peptides. Due to their widespread use, it is now time to perform a systematic analysis of the various algorithms currently in use. Using blood specimens used in the HUPO Plasma Proteome Project, we have evaluated five search algorithms with respect to their sensitivity and specificity, and have also accurately benchmarked them based on specified false-positive (FP) rates. Spectrum Mill and SEQUEST performed well in terms of sensitivity, but were inferior to MASCOT, X!Tandem, and Sonar in terms of specificity. Overall, MASCOT, a probabilistic search algorithm, correctly identified most peptides based on a specified FP rate. The rescoring algorithm, PeptideProphet, enhanced the overall performance of the SEQUEST algorithm, as well as provided predictable FP error rates. Ideally, score thresholds should be calculated for each peptide spectrum or minimally, derived from a reversed-sequence search as demonstrated in this study based on a validated data set. The availability of open-source search algorithms, such as X!Tandem, makes it feasible to further improve the validation process (manual or automatic) on the basis of "consensus scoring", i.e., the use of multiple (at least two) search algorithms to reduce the number of FPs. complement.     

Cysteineless non-glycosylated monomeric blue fluorescent protein,secBFP2, for studies in the eukaryotic secretory pathway

Fluorescent protein (FP) technologies suitable for use within the eukaryotic secretory pathway are essential for live cell and protein dynamic studies. Localization of FPs within the endoplasmic reticulum (ER) lumen has potentially significant consequences for FP function. All FPs are resident cytoplasmic proteins and have rarely been evolved for the chemically distinct environment of the ER lumen. In contrast to the cytoplasm, the ER lumen is oxidizing and the site where secretory proteins are post-translationally modified by disulfide bond formation and N-glycosylation on select asparagine residues. Cysteine residues and N-linked glycosylation consensus sequences were identified within many commonly utilized FPs. Here, we report mTagBFP is post-translationally modified when localized to the ER lumen. Our findings suggest these modifications can grossly affect the sensitivity and reliability of FP tools within the secretory pathway. To optimize tools for studying events in this important intracellular environment, we modified mTagBFP by mutating its cysteines and consensus N-glycosylation sites. We report successful creation of a secretory pathway-optimized blue FP, secBFP2.     

Enhanced Syllable Discrimination Thresholds in Musicians

Speech processing inherently relies on the perception of specific, rapidly changing spectral and temporal acoustic features. Advanced acoustic perception is also integral to musical expertise, and accordingly several studies have demonstrated a significant relationship between musical training and superior processing of various aspects of speech. Speech and music appear to overlap in spectral and temporal features; however, it remains unclear which of these acoustic features, crucial for speech processing, are most closely associated with musical training. The present study examined the perceptual acuity of musicians to the acoustic components of speech necessary for intra-phonemic discrimination of synthetic syllables. We compared musicians and non-musicians on discrimination thresholds of three synthetic speech syllable continua that varied in their spectral and temporal discrimination demands, specifically voice onset time (VOT) and amplitude envelope cues in the temporal domain. Musicians demonstrated superior discrimination only for syllables that required resolution of temporal cues. Furthermore, performance on the temporal syllable continua positively correlated with the length and intensity of musical training. These findings support one potential mechanism by which musical training may selectively enhance speech perception, namely by reinforcing temporal acuity and/or perception of amplitude rise time, and implications for the translation of musical training to long-term linguistic abilities.     

Negatively charged residues in the membrane ordering activity of SARS-CoV-1 and -2 fusion peptides

Entry of coronaviruses into host cells is mediated by the viral spike protein. Previously, we identified the bona fide fusion peptides (FPs) for severe acute respiratory syndrome coronavirus (“SARS-1”) and severe acute respiratory syndrome coronavirus-2 (“SARS-2”) using electron spin resonance spectroscopy. We also found that their FPs induce membrane ordering in a Ca²⁺-dependent fashion. Here we study which negatively charged residues in SARS-1 FP are involved in this binding, to build a topological model and clarify the role of Ca²⁺. Our systematic mutation study on the SARS-1 FP shows that all six negatively charged residues contribute to the FP’s membrane ordering activity, with D812 the dominant residue. The corresponding SARS-2 residue D830 plays an equivalent role. We provide a topological model of how the FP binds Ca²⁺ ions: its two segments FP1 and FP2 each bind one Ca²⁺. The binding of Ca²⁺, the folding of FP (both studied by isothermal titration calorimetry experiments), and the ordering activity correlate very well across the mutants, suggesting that the Ca²⁺ helps the folding of FP in membranes to enhance the ordering activity. Using a novel pseudotyped viral particle-liposome methodology, we monitored the membrane ordering induced by the FPs in the whole spike protein in its trimer form in real time. We found that the SARS-1 and SARS-2 pseudotyped viral particles also induce membrane ordering to the extent that separate FPs do, and mutations of the negatively charged residues also significantly suppress the membrane ordering activity. However, the slower kinetics of the FP ordering activity versus that of the pseudotyped viral particle suggest the need for initial trimerization of the FPs.     

Automatic detection of false annotations via binary property clustering

Background  

Computational protein annotation methods occasionally introduce errors. False-positive (FP) errors are annotations that are mistakenly associated with a protein. Such false annotations introduce errors that may spread into databases through similarity with other proteins. Generally, methods used to minimize the chance for FPs result in decreased sensitivity or low throughput. We present a novel protein-clustering method that enables automatic separation of FP from true hits. The method quantifies the biological similarity between pairs of proteins by examining each protein's annotations, and then proceeds by clustering sets of proteins that received similar annotation into biological groups.     

Continuous ambulatory hand force monitoring during manual materials handling using instrumented force shoes and an inertial motion capture suit

Hand forces (HFs) are commonly measured during biomechanical assessment of manual materials handling; however, it is often a challenge to directly measure HFs in field studies. Therefore, in a previous study we proposed a HF estimation method based on ground reaction forces (GRFs) and body segment accelerations and tested it with laboratory equipment: GFRs were measured with force plates (FPs) and segment accelerations were measured using optical motion capture (OMC). In the current study, we evaluated the HF estimation method based on an ambulatory measurement system, consisting of inertial motion capture (IMC) and instrumented force shoes (FSs).Sixteen participants lifted and carried a 10-kg crate from ground level while 3D full-body kinematics were measured using OMC and IMC, and 3D GRFs were measured using FPs and FSs. We estimated 3D hand force vectors based on: (1) FP+OMC, (2) FP+IMC and (3) FS+IMC. We calculated the root-mean-square differences (RMSDs) between the estimated HFs to reference HFs calculated based on crate kinematics and the GRFs of a FP that the crate was lifted from.Averaged over subjects and across 3D force directions, the HF RMSD ranged between 10-15N when using the laboratory equipment (FP + OMC), 11-18N when using the IMC instead of OMC data (FP+IMC), and 17-21N when using the FSs in combination with IMC (FS + IMC). This error is regarded acceptable for the assessment of spinal loading during manual lifting, as it would results in less than 5% error in peak moment estimates.     

Coral Fluorescent Proteins as Antioxidants

Background

A wide array of fluorescent proteins (FP) is present in anthozoans, although their biochemical characteristics and function in host tissue remain to be determined. Upregulation of FP''s frequently occurs in injured or compromised coral tissue, suggesting a potential role of coral FPs in host stress responses.

Methodology/Principal Findings

The presence of FPs was determined and quantified for a subsample of seven healthy Caribbean coral species using spectral emission analysis of tissue extracts. FP concentration was correlated with the in vivo antioxidant potential of the tissue extracts by quantifying the hydrogen peroxide (H₂O₂) scavenging rates. FPs of the seven species varied in both type and abundance and demonstrated a positive correlation between H₂O₂ scavenging rate and FP concentration. To validate this data, the H₂O₂ scavenging rates of four pure scleractinian FPs, cyan (CFP), green (GFP), red (RFP) and chromoprotein (CP), and their mutant counterparts (without chromophores), were investigated. In vitro, each FP scavenged H₂O₂ with the most efficient being CP followed by equivalent activity of CFP and RFP. Scavenging was significantly higher in all mutant counterparts.

Conclusions/Significance

Both naturally occurring and pure coral FPs have significant H₂O₂ scavenging activity. The higher scavenging rate of RFP and the CP in vitro is consistent with observed increases of these specific FPs in areas of compromised coral tissue. However, the greater scavenging ability of the mutant counterparts suggests additional roles of scleractinian FPs, potentially pertaining to their color. This study documents H₂O₂ scavenging of scleractinian FPs, a novel biochemical characteristic, both in vivo across multiple species and in vitro with purified proteins. These data support a role for FPs in coral stress and immune responses and highlights the multi-functionality of these conspicuous proteins.     

Multi-domain GFP-like proteins from two species of marine hydrozoans

Proteins homologous to Green Fluorescent Protein (GFP) are widely used as genetically encoded fluorescent labels. Many developments of this technology were spurred by discoveries of novel types of GFP-like proteins (FPs) in nature. Here we report two proteins displaying primary structures never before encountered in natural FPs: they consist of multiple GFP-like domains repeated within the same polypeptide chain. A two-domain green FP (abeGFP) and a four-domain orange-fluorescent FP (Ember) were isolated from the siphonophore Abylopsis eschscholtzii and an unidentified juvenile jellyfish (order Anthoathecata), respectively. Only the most evolutionary ancient domain of Ember is able to synthesize an orange-emitting chromophore (emission at 571 nm), while the other three are purely green (emission at 520 nm) and putatively serve to maintain the stability and solubility of the multidomain protein. When expressed individually, two of the green Ember domains form dimers and the third one exists as a monomer. The low propensity for oligomerization of these domains would simplify their adoption as in vivo labels. Our results reveal a previously unrecognized direction in which natural FPs have diversified, suggesting new avenues to look for FPs with novel and potentially useful features.     

Fluorescent proteins for FRET microscopy: monitoring protein interactions in living cells

The discovery and engineering of novel fluorescent proteins (FPs) from diverse organisms is yielding fluorophores with exceptional characteristics for live-cell imaging. In particular, the development of FPs for fluorescence (or F?rster) resonance energy transfer (FRET) microscopy is providing important tools for monitoring dynamic protein interactions inside living cells. The increased interest in FRET microscopy has driven the development of many different methods to measure FRET. However, the interpretation of FRET measurements is complicated by several factors including the high fluorescence background, the potential for photoconversion artifacts and the relatively low dynamic range afforded by this technique. Here, we describe the advantages and disadvantages of four methods commonly used in FRET microscopy. We then discuss the selection of FPs for the different FRET methods, identifying the most useful FP candidates for FRET microscopy. The recent success in expanding the FP color palette offers the opportunity to explore new FRET pairs.     

Spectrally-Resolved Response Properties of the Three Most Advanced FRET Based Fluorescent Protein Voltage Probes

Genetically-encoded optical probes for membrane potential hold the promise of monitoring electrical signaling of electrically active cells such as specific neuronal populations in intact brain tissue. The most advanced class of these probes was generated by molecular fusion of the voltage sensing domain (VSD) of Ci-VSP with a fluorescent protein (FP) pair. We quantitatively compared the three most advanced versions of these probes (two previously reported and one new variant), each involving a spectrally distinct tandem of FPs. Despite these different FP tandems and dissimilarities within the amino acid sequence linking the VSD to the FPs, the amplitude and kinetics of voltage dependent fluorescence changes were surprisingly similar. However, each of these fluorescent probes has specific merits when considering different potential applications.     

The influenza fusion peptide promotes lipid polar head intrusion through hydrogen bonding with phosphates and N‐terminal membrane insertion depth

Influenza infection requires fusion between the virus envelope and a host cell endosomal membrane. The influenza hemagglutinin fusion peptide (FP) is essential to viral membrane fusion. It was recently proposed that FPs would fuse membranes by increasing lipid tail protrusion, a membrane fusion transition state. The details of how FPs induce lipid tail protrusion, however, remain to be elucidated. To decipher the molecular mechanism by which FPs promote lipid tail protrusion, we performed molecular dynamics simulations of the wild‐type (WT) FP, fusogenic mutant F9A, and nonfusogenic mutant W14A in model bilayers. This article presents the peptide–lipid interaction responsible for lipid tail protrusion and a related lipid perturbation, polar head intrusion, where polar heads are sunk under the membrane surface. The backbone amides from the four N‐terminal peptide residues, deeply inserted in the membrane, promoted both perturbations through H bonding with lipid phosphates. Polar head intrusion correlated with peptides N‐terminal insertion depth and activity: the N‐termini of WT and F9A were inserted deeper into the membrane than nonfusogenic W14A. Based on these results, we propose that FP‐induced polar head intrusion would complement lipid tail protrusion in catalyzing membrane fusion by reducing repulsions between juxtaposed membranes headgroups. The presented model provides a framework for further research on membrane fusion and influenza antivirals. Proteins 2014; 82:2118–2127. © 2014 Wiley Periodicals, Inc.     

Design of near-infrared single-domain fluorescent protein GAF-FP based on bacterial phytochrome

Fluorescent proteins (FPs) are widely used as genetically encoded markers for quantitative and noninvasive study of biological processes. Development of biomarkers that are fluorescent in the near-infrared spectral range allows the tissues of animals to be studied at a deeper level because they are more permeable to the light of this wavelength range than that of visible range. Such properties as low molecular weight and monomeric state are important for widespread use of FPs. In this paper, we managed to obtain FP based on the chromophore-binding domain of bacterial phytochrome (BphP) from Rhodopseudomonas palustris (RpB-phP1), named GAF-FP, with a molecular weight of ~19 kDa, which is half that of other FP based on BphP and 1.4 times lower than that of commonly used GFP-like proteins, which are fluorescent in the near-infrared range. In contrast to most other near-infrared FPs, GAF-FP is a monomer, which has a high photostability, and its structure is stable to the incorporation of small peptide inserts. Moreover, GAF-FP is capable of covalent attachment of two different tetrapyrrole chromophores: phycocyanobilin (PCB) and biliverdin (BV), which is contained in mammalian tissues. GAF-FP with attached BV as a chromophore (GAF-FP–BV) has the main absorption band with a maximum at 635 nm. The fluorescence maximum falls at 670 nm, whereby GAF-FP has a high ratio of the fluorescence signal to the background signal even if FP is localized at a depth of several mm below the tissue surface. Together with the near-infrared absorption band, GAF-FP–BV also has an absorption band in the violet region of the spectrum with a maximum at 378 nm. We used this property to design a chimeric protein consisting of modified luciferase from Renilla reniformis (RLuc8) and GAF-FP. We showed resonance energy transfer from the substrate, the excited state of which occurs when oxidized by luciferase, to the chromophore GAF-FP–BV in the designed fusion protein. In the absence of an energy acceptor, RLuc8 catalyzes the cleavage of the substrate with the emission of the light with a maximum at 400 nm. At the same time, the energy from the substrate is transferred to the FP chromophore and then emitted in the near-infrared range corresponding to the spectrum of GAF-FP fluorescence in the GAF-FP–RLuc8 chimeric protein. These results open the way for the development of new small near-infrared FPs based on various natural BphPs with a view to their widespread use in cell and molecular biology.     

Family physician workloads and access to care in Winnipeg: 1991 to 2001

Background

Current perceptions of family physician (FP) shortages in Canada have prompted policies to expand medical schools. Our objective was to assess how FP supply, workloads and access to care have changed over the past decade.

Methods

We used an anonymized physician and population registry and administrative health service data from Winnipeg for the period 1991/92 to 2000/01. We calculated the following measures of supply and workload: ratios of FPs to population, of population to FPs and of FP full-time equivalents (FTEs) to population, as well as FP activity ratios (sum of FTEs/number of FPs), annual number of visits per FP and visits per FP per full-time day of work. Trends in FP remuneration were analyzed by age and sex. We also measured standardized visit rates and stratified the analysis by populations deemed at risk of needing FP services.

Results

In 2000/01 FPs between 30 and 49 years of age (64% of the workforce) provided 20% fewer visits per year than their same-age peers did 10 years previously. Conversely, FPs 60 to 69 years of age (11% of the workforce) provided 33% more visits per year than the corresponding group a decade earlier. On a per capita basis, the number of FPs declined by 5%, from 97 per 100 000 population in 1991/92 to 92 per 100 000 population in 2000/01, which paralleled changes in national estimates of FP supply. Per capita visit rates among Winnipeg citizens (3.5 per year in 2000/01) and average workloads among FPs (4193 visits per year in 2000/01) were stable over the decade.

Interpretation

Despite relative homeostasis in aggregate FP supply and use, there have been substantial temporal shifts in the volume of services provided by FPs of different age groups. Younger FPs are providing many fewer visits and older FPs are providing many more visits than their same-age predecessors did 10 years ago, a finding that was independent of physician sex. Given these data, the perpetual focus of policy-makers and care providers on increasing numbers of FPs will not help in diagnosing or treating issues of supply, workloads and access to care.In 2002, 80% of Canadians believed that there was a shortage of “family doctors,” and 97% of these people believed that the shortage was serious.¹ These perceptions are amplified within the physician workforce itself, with 93% of physicians surveyed in the same year believing that shortages among their ranks were widespread.² Paradoxically, current perceptions of shortages and suggestions to fast-track increases in supply^3,4 come close on the heels of widespread perceptions of surpluses, at least in urban centres, and reductions in medical school enrolment only 10 years ago. For example, in 1993, a Canadian Medical Association survey found that half of the doctors in the country believed enrolment in medical schools should be reduced.⁵ Such relatively quick shifts from perceptions of surpluses to ones of shortages are at odds with recent national data indicating that the per capita number of FPs has remained relatively stable over the last decade.^6,7Unfortunately, temporal patterns of FP workloads over the past decade have not been documented in national supply-side analyses.^6,8 Furthermore, analyses have not been conducted to understand temporal patterns in the relation between FP age or sex and workloads. Yet this type of information is vital to understanding (and projecting) the impact of demographic shifts in the workforce⁸ on current (and future) supply of services. When the supply of FPs is inadequate, the workloads of both FPs and specialists could be affected and access to care compromised. There is evidence that FPs work long hours,⁹ that many are unhappy with their workloads^9,10 and that those who report heavy workloads are more likely than others to stop accepting new patients.⁶The purposes of this study were to evaluate whether FP workloads, on average or for certain cohorts of practitioners, have changed over a period of relatively stable FP-to-population ratios; to simultaneously examine the population''s use of FPs; and to consider the potential impact of any change in workloads or service utilization on perceptions of adequacy of FP supply and access to care. This population-based study, which formed part of a larger project,¹¹ was based on data from Winnipeg, a city (like others in Canada) where FPs report unhappiness with workloads, where citizens express frustration regarding access to FPs and where journalists document widely held views that many FP practices are “restricted” in accepting new patients.¹² We hypothesized that average workloads increased, that population rates of use declined, and that age- and sex-specific workloads remained constant.     

Automatic detection of voice impairments from text-dependent running speech

Acoustic analysis is a useful tool to diagnose voice diseases. Furthermore it presents several advantages: it is non-invasive, provides an objective diagnostic and, also, it can be used for the evaluation of surgical and pharmacological treatments and rehabilitation processes. Most of the approaches found in the literature address the automatic detection of voice impairments from speech by using the sustained phonation of vowels. In this paper it is proposed a new scheme for the detection of voice impairments from text-dependent running speech. The proposed methodology is based on the segmentation of speech into voiced and non-voiced frames, parameterising each voiced frame with mel-frequency cepstral parameters. The classification is carried out using a discriminative approach based on a multilayer perceptron neural network. The data used to train the system were taken from the voice disorders database distributed by Kay Elemetrics. The material used for training and testing contains the running speech corresponding to the well known “rainbow passage” of 140 patients (23 normal and 117 pathological). The results obtained are compared with those using sustained vowels. The text-dependent running speech showed a light improvement in the accuracy of the detection.     

Interactions of SARS-CoV-2 and MERS-CoV fusion peptides measured using single-molecule force methods

We address the challenge of understanding how hydrophobic interactions are encoded by fusion peptide (FP) sequences within coronavirus (CoV) spike proteins. Within the FPs of severe acute respiratory syndrome CoV 2 and Middle East respiratory syndrome CoV (MERS-CoV), a largely conserved peptide sequence called FP1 (SFIEDLLFNK and SAIEDLLFDK in SARS-2 and MERS, respectively) has been proposed to play a key role in encoding hydrophobic interactions that drive viral-host cell membrane fusion. Although a non-polar triad (Leu-Leu-Phe (LLF)) is common to both FP1 sequences, and thought to dominate the encoding of hydrophobic interactions, FP1 from SARS-2 and MERS differ in two residues (Phe 2 versus Ala 2 and Asn 9 versus Asp 9, respectively). Here we explore whether single-molecule force measurements can quantify hydrophobic interactions encoded by FP1 sequences, and then ask whether sequence variations between FP1 from SARS-2 and MERS lead to significant differences in hydrophobic interactions. We find that both SARS-2 and MERS wild-type FP1 generate measurable hydrophobic interactions at the single-molecule level, but that SARS-2 FP1 encodes a substantially stronger hydrophobic interaction than its MERS counterpart (1.91 ± 0.03 nN versus 0.68 ± 0.03 nN, respectively). By performing force measurements with FP1 sequences with single amino acid substitutions, we determine that a single-residue mutation (Phe 2 versus Ala 2) causes the almost threefold difference in the hydrophobic interaction strength generated by the FP1 of SARS-2 versus MERS, despite the presence of LLF in both sequences. Infrared spectroscopy and circular dichroism measurements support the proposal that the outsized influence of Phe 2 versus Ala 2 on the hydrophobic interaction arises from variation in the secondary structure adopted by FP1. Overall, these insights reveal how single-residue diversity in viral FPs, including FP1 of SARS-CoV-2 and MERS-CoV, can lead to substantial changes in intermolecular interactions proposed to play a key role in viral fusion, and hint at strategies for regulating hydrophobic interactions of peptides in a range of contexts.