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1. Structural and genetic basis for the binding of a mouse monoclonal antibody to Flavobacterium psychrophilum lipopolysaccharide

   https://doi.org/10.1111/jfd.13958  

   Cisar, John O; Wang, Xiaocong; Woods, Robert J; Cain, Kenneth D; Wiens, Gregory D (June 2024, Journal of Fish Diseases)

   Abstract A mouse monoclonal antibody (mAb FL100A) previously prepared againstFlavobacterium psychrophilum(Fp) CSF259‐93 has now been examined for binding to lipopolysaccharides (LPS) of this strain andFp950106‐1/1. The corresponding O‐polysaccharides (O‐PS) of these strains are formed by identical trisaccharide repeats composed ofl‐Rhamnose (l‐Rha), 2‐acetamido‐2‐deoxy‐l‐fucose (l‐FucNAc) and 2‐acetamido‐4‐R₁‐2,4‐dideoxy‐d‐quinovose (d‐Qui2NAc4NR₁) where R₁represents a dihydroxyhexanamido moiety. The O‐PS loci of these strains are also identical except for the gene (wzy1orwzy2) that encodes the polysaccharide polymerase. Accordingly, adjacent O‐PS repeats are joined throughd‐Qui2NAc4NR₁andl‐Rha bywzy2‐dependent α(1–2) linkages inFpCSF259‐93 versuswzy1‐dependent β(1–3) linkages inFp950106‐1/1. mAb FL100A reacted strongly withFpCSF259‐93 O‐PS and LPS but weakly or not at all withFp950106‐1/1 LPS and O‐PS. Importantly, it also labelled cell surface blebs on the former but not the latter strain. Additionally, mAb binding was approximately 5‐times stronger to homologousFpCSF259‐93 LPS than to LPS from a strain with a different R‐group gene. A conformational epitope for mAb FL100A binding was suggested from molecular dynamic simulations of each O‐PS. Thus,FpCSF259‐93 O‐PS formed a stable well‐defined compact helix in which the R₁groups were displayed in a regular pattern on the helix exterior while unreactiveFp950106‐1/1 O‐PS adopted a flexible extended linear conformation. Taken together, the findings establish the specificity of mAb FL100A for Wzy2‐linkedF. psychrophilumO‐PS and LPS. 

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2. Ward identities for superamplitudes

   https://doi.org/10.1007/JHEP06(2024)035  

   Kallosh, Renata (June 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> We introduce Ward identities for superamplitudes inD-dimensional$$ \mathcal{N} $$ $N$ -extended supergravities. These identities help to clarify the relation between linearized superinvariants and superamplitudes. The solutions of these Ward identities for ann-partice superamplitude take a simple universal form for half BPS and non-BPS amplitudes. These solutions involve arbitrary functions of spinor helicity and Grassmann variables for each of thensuperparticles. The dimension of these functions at a given loop order is exactly the same as the dimension of the relevant superspace Lagrangians depending on half-BPS or non-BPS superfields, given by (D− 2)L+ 2 −$$ \mathcal{N} $$ $N$ or (D− 2)L+ 2 −$$ 2\mathcal{N} $$ $2N$ , respectively. This explains why soft limits predictions from superamplitudes and from superspace linearized superinvariants agree. 

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3. In Vitro Biosynthesis of the Nonproteinogenic Amino Acid Methoxyvinylglycine

   https://doi.org/10.1002/anie.201713419  

   Patteson, Jon B.; Dunn, Zachary D.; Li, Bo (June 2018, Angewandte Chemie International Edition)

   Abstract Oxyvinylglycines are a family of nonproteinogenic amino acids featuring an essential vinyl ether conferring mechanism‐based inhibition of pyridoxal phosphate enzymes. The gene clusters for a few oxyvinylglycines are known, yet the biosynthetic origin of the vinyl ether is elusive. The in vitro biosynthesis of methoxyvinylglycine orl‐2‐amino‐4‐methoxy‐trans‐3‐butenoic acid (AMB) is reported. It is shown that AMB is made from glutamate as an alanyl‐AMB dipeptide and the rationale is provided for the N‐term Ala. Using a chemical capture method, the order and timing of the modifications on non‐ribosomal peptide synthetase (NRPS)‐bound substrates was determined, including a cryptic hydroxylation of the Glu β‐carbon. Eliminating this hydroxy group likely generates a key α,β‐dehydroamino acid intermediate that facilitates decarboxylation. This work sheds light on vinyl ether biosynthesis and uncovers new NRPS chemistry. 

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4. Hydrogen-poor Superluminous Supernovae in the Nebular Phase: Spectral Diversity Due to Ejecta Ionization as a Probe of the Power Source

   https://doi.org/10.3847/1538-4357/ae3d09  

   Blanchard, Peter K; Berger, Edo; Gomez, Sebastian; Nicholl, Matt; Chornock, Ryan; Kumar, Harsh; Margutti, Raffaella; Hiramatsu, Daichi; Sears, Huei (February 2026, The Astrophysical Journal)

   Abstract We present a large sample of 39 nebular-phase optical spectra of 25 hydrogen-poor superluminous supernovae (SLSNe-I) and jointly analyze them with previously published spectra of 12 events. We measure the properties of key emission features, namely, those at 6300, 7300, and 7774 Å (associated with [Oi], [Caii]/[Oii], and Oi, respectively), and find that SLSNe exhibit much wider spectral diversity than normal SNe Ic, primarily in the line ratioL₇₃₀₀/L₆₃₀₀, which is highly sensitive to ejecta ionization. Some events exhibit weak [Oi] and a clear [Oii] contribution to the 7300 Å feature, enhancing the ratio, along with [Oiii] lines at 4363 and 5007 Å. Other SLSNe show weak or no lines of ionized oxygen. Moreover, we find that the population exhibits decreasingL₇₃₀₀/L₆₃₀₀over time, while a few outliers instead display sustained high or increasing ratios for extended periods. The ratioL₇₃₀₀/L₆₃₀₀is also correlated with the rise and decline times of the light curves, with slower events exhibiting higher ionization, the first robust connection between early light-curve and late-time spectral properties, likely due to the magnetar’s impact: slower-evolving SLSNe are generally powered by engines with longer spin-down timescales, which deposit more energy at later phases. Among the events with decreasingL₇₃₀₀/L₆₃₀₀, SLSNe with high ionization are on average powered by magnetars with higher thermalized spin-down power, a correlation that is most significant for events withM_ej ≲ 12M_⊙. The ionization in the outliers with increasingL₇₃₀₀/L₆₃₀₀may be due to late circumstellar medium interaction.L₇₃₀₀/L₆₃₀₀and its evolution are therefore key diagnostics of SLSN engines and progenitor mass loss. 

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5. Adaptive Laboratory Evolution of Probiotics toward Oxidative Stress Using a Microfluidic‐Based Platform

   https://doi.org/10.1002/smll.202306974  

   Nguyen, Ann V; Yaghoobi, Mohammad; Zhang, Shiying; Li, Peilong; Li, Qike; Dogan, Belgin; Ahnrud, Gianna P; Flock, Genevieve; Marek, Patrick; Simpson, Kenneth W; et al (June 2024, Small)

   Abstract Adaptive laboratory evolution (ALE) can be used to make bacteria less susceptible to oxidative stress. An alternative to large batch scale ALE cultures is to use microfluidic platforms, which are often more economical and more efficient. Microfluidic ALE platforms have shown promise, but many have suffered from subpar cell passaging mechanisms and poor spatial definition. A new approach is presented using a microfluidic Evolution on a Chip (EVoc) design which progressively drives microbial cells from areas of lower H₂O₂concentration to areas of higher concentration. Prolonged exposure, up to 72 h, revealed the survival of adaptive strains ofLacticaseibacillus rhamnosusGG, a beneficial probiotic often included in food products. After performing ALE on this microfluidic platform, the bacteria persisted under high H₂O₂concentrations in repeated trials. After two progressive exposures, the ability ofL. rhamnosusto grow in the presence of H₂O₂increased from 1 mmH₂O₂after a lag time of 31 h to 1 mmafter 21 h, 2 mmafter 28 h, and 3 mmafter 42 h. The adaptive strains have different morphology, and gene expression compared to wild type, and genome sequencing revealed a potentially meaningful single nucleotide mutation in the protein omega‐amidase. 

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