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The spread of multidrug-resistant strains of Neisseria gonorrhoeae, the etiologic agent of gonorrhea, represents a global health emergency. Therefore, the development of a safe and effective vaccine against gonorrhea is urgently needed. In previous studies, murine monoclonal antibody (mAb) 2C7 was raised against gonococcal lipooligosaccharide (LOS). mAb 2C7 elicits complement-dependent bactericidal activity against gonococci, and its glycan epitope is expressed by almost every clinical isolate. Furthermore, we identified a peptide, cyclic peptide 2 (CP2) that mimicked the 2C7 LOS epitope, elicited bactericidal antibodies in mice, and actively protected in a mouse vaginal colonization model. In this study, we performed structural analyses of mAb 2C7 and its complex with the CP2 peptide by X-ray crystallography, NMR spectroscopy, and molecular dynamics (MD) simulations. The crystal structure of Fab 2C7 bound to CP2 showed that the peptide adopted a beta-hairpin conformation and bound the Fab primarily through hydrophobic interactions. We employed NMR spectroscopy and MD simulations to map the 2C7 epitope and identify the bioactive conformation of CP2. We also used small-angle X-ray scattering (SAXS) and native mass spectrometry to obtain further information about the shape and assembly state of the complex. Collectively, our new structural information suggests strategies for humanizing mAb 2C7 as a therapeutic against gonococcal infection and for optimizing peptide CP2 as a vaccine antigen.

Photoinduced manipulation of the nanoscale molecular structure and organization of soft materials can drive changes in the macroscale properties. Here we demonstrate the first example of a light-induced one- to three-dimensional mesophase transition at room temperature in lyotropic liquid crystals constructed from arylazopyrazole photosurfactants in water. We exploit this characteristic to use light to selectively control the rate of gas (CO2) diffusion across a prototype lyotropic liquid crystal membrane. Such control of phase organization, dimensionality, and permeability unlocks the potential for stimuli-responsive analogues in technologies for controlled delivery.

The self-assembly of an arylazopyrazole-based photosurfactant (PS), based on cetyltrimethylammonium bromide (CTAB), and its mixed micelle formation with CTAB in aqueous solution was investigated by small angle neutron and X-ray scattering (SANS/SAXS) and UV–vis absorption spectroscopy. Upon UV light exposure, PS photoisomerizes from E-PS (trans) to Z-PS (cis), which transforms oblate ellipsoidal micelles into smaller, spherical micelles with larger shell thickness. Doping PS with CTAB resulted in mixed micelle formation at all stoichiometries and conditions investigated; employing selectively deuterated PS, a monotonic variation in scattering length density and dimensions of the micellar core and shell is observed for all contrasts. The concentration- and irradiance-dependence of the Eto Zconfigurational transition was established in both neat and mixed micelles. A liposome dye release assay establishes the enhanced efficacy of photosurfactants at membrane disruption, with E-PS exhibiting a 4-fold and Z-PS a 10-fold increase in fluorescence signal with respect to pure CTAB. Our findings pave the way for external triggering and modulation of the wide range of CTAB-based biomedical and material applications.

Biofermentative production of styrene from renewable carbon sources is crucially dependent on strain tolerance and viability at elevated styrene concentrations. Solvent-driven collapse of bacterial plasma membranes limits yields and is technologically restrictive. Styrene is a hydrophobic solvent that readily partitions into the membrane interior and alters membrane-chain order and packing. We investigate styrene incorporation into model membranes and the role lipid chains play as determinants of membrane stability in the presence of styrene. MD simulations reveal styrene phase separation followed by irreversible segregation into the membrane interior. Solid state NMR shows committed partitioning of styrene into the membrane interior with persistence of the bilayer phase up to 67 mol % styrene. Saturated-chain lipid membranes were able to retain integrity even at 80 mol % styrene, whereas in unsaturated lipid membranes, we observe the onset of a non-bilayer phase of small lipid aggregates in coexistence with styrene-saturated membranes. Shorter-chain saturated lipid membranes were seen to tolerate styrene better, which is consistent with observed chain length reduction in bacteria grown in the presence of small molecule solvents. Unsaturation at mid-chain position appears to reduce the membrane tolerance to styrene and conversion from cis- to trans-chain unsaturation does not alter membrane phase stability but the lipid order in trans-chains is less affected than cis.

Polyelectrolyte–surfactant complexes (PESCs) are important soft colloids with applications in the fields of personal care, cosmetics, pharmaceutics, and much more. If their phase diagrams have long been studied under pseudoequilibrium conditions, and often inside the micellar or vesicular regions, understanding the effect of nonequilibrium conditions, applied at phase boundaries, on the structure of PESCs generates an increasing interest. In this work we cross the micelle–vesicle and micelle–fiber phase boundaries in an isocompositional surfactant–polyelectrolyte aqueous system through a continuous and rapid variation of pH. We employ two microbial glycolipid biosurfactants in the presence of polyamines, both systems being characterized by their responsiveness to pH. We show that complex coacervates (Co) are always formed in the micellar region of both glycolipids’ phase diagram and that their phase behavior drives the PESC stability and structure. However, for glycolipid forming single-wall vesicles, we observe an isostructural and isodimensional transition between complex coacervates and a multilamellar walls vesicle (MLWV) phase. For the fiber-forming glycolipid, on the contrary, the complex coacervate disassembles into free polyelectrolyte coexisting with the equilibrium fiber phase. Last but not least, this work also demonstrates the use of microbial glycolipid biosurfactants in the development of sustainable PESCs.

It is common to switch between H2O and D2O when examining peptide-based systems, with the assumption being that there are no effects from this change. Here, we describe the effect of changing from H2O to D2O in a number of low-molecular-weight dipeptide-based gels. Gels are formed by decreasing the pH. In most cases, there is little difference in the structures formed at high pH, but this is not universally true. On lowering the pH, the kinetics of gelation are affected and, in some cases, the structures underpinning the gel network are different. Where there are differences in the self-assembled structures, the resulting gel properties are different. We, therefore, show that isotopic control over gel properties is possible.

Stimuli-responsive materials are crucial to advance controlled delivery systems for drugs and catalysts. Lyotropic liquid crystals (LLCs) have well-defined internal structures suitable to entrap small molecules and can be broken up into low-viscosity dispersions, aiding their application as delivery systems. In this work, we demonstrate the first example of light-responsive cubic LLC dispersions, or cubosomes, using photoswitchable amphiphiles to enable external control over the LLC structure and subsequent on-demand release of entrapped guest molecules. Azobenzene photosurfactants (AzoPS), containing a neutral tetraethylene glycol head group and azobenzene-alkyl tail, are combined (from 10–30 wt %) into monoolein-water systems to create LLC phases. Homogenization of the bulk LLC forms dispersions of particles, ∼200 nm in diameter with internal bicontinuous primitive cubic phases, as seen using small-angle X-ray scattering and cryo-transmission electron microscopy. Notably, increasing the AzoPS concentration leads to swelling of the cubic lattice, offering a method to tune the internal nanoscale structure. Upon UV irradiation, AzoPS within the cubosomes isomerizes within seconds, which in turn leads to squeezing of the cubic lattice and a decrease in the lattice parameter. This squeeze mechanism was successfully harnessed to enable phototriggerable release of trapped Nile Red guest molecules from the cubosome structure in minutes. The ability to control the internal structure of LLC dispersions using light, and the dramatic effect this has on the retention of entrapped molecules, suggests that these systems may have huge potential for the next-generation of nanodelivery.

Plasminogen is the proenzyme precursor of the primary fibrinolytic protease plasmin. Circulating plasminogen, which comprises a Pan-apple (PAp) domain, five kringle domains (KR1-5), and a serine protease (SP) domain, adopts a closed, activation-resistant conformation. The kringle domains mediate interactions with fibrin clots and cell-surface receptors. These interactions trigger plasminogen to adopt an open form that can be cleaved and converted to plasmin by tissue-type and urokinase-type plasminogen activators. Here, the structure of closed plasminogen reveals that the PAp and SP domains, together with chloride ions, maintain the closed conformation through interactions with the kringle array. Differences in glycosylation alter the position of KR3, although in all structures the loop cleaved by plasminogen activators is inaccessible. The ligand-binding site of KR1 is exposed and likely governs proenzyme recruitment to targets. Furthermore, analysis of our structure suggests that KR5 peeling away from the PAp domain may initiate plasminogen conformational change.