Structural Antagonism-Aided Conformational Regulation Enables an Aptamer-Loop G-Quadruplex Modular Sensor of ß-Lactoglobulin.

A simple, reliable method for identifying ß-lactoglobulin (ß-LG) in dairy products is needed to protect those with ß-LG allergies. A common, practical strategy for target detection is designing simplified nucleic acid nanodevices by integrating functional components. This work presents a label-free modular ß-LG aptasensor consisting of an aptamer-loop G-quadruplex (G4), the working conformation of which is regulated by conformational antagonism to ensure respective module functionality and the related signal transduction. The polymorphic conformations of the module-fused sequence are systematically characterized, and the cause is revealed as shifting antagonistic equilibrium. Combined with conformational folding dynamics, this helped regulate functional conformations by fine-tuning the sequences. Furthermore, the principle of specific ß-LG detection by parallel G4 topology is examined as binding on the G4 aptamer loop by ß-LG to reinforce the G4 topology and fluorescence. Finally, a label-free, assembly-free, succinct, and turn-on fluorescent aptasensor is established, achieving excellent sensitivity across five orders of magnitude, rapidly detecting ß-LG within 22-min. This study provides a generalizable approach for the conformational regulation of module-fused G4 sequences and a reference model for creating simplified sensing devices for a variety of targets.

Construction Strategy of Functionalized Liposomes and Multidimensional Application.

Liposomes are widely used in the biological field due to their good biocompatibility and surface modification properties. With the development of biochemistry and material science, many liposome structures and their surface functional components have been modified and optimized one by one, pushing the liposome platform from traditional to functionalized and intelligent, which will better satisfy and expand the needs of scientific research. However, a main limiting factor effecting the efficiency of liposomes is the complicated environmental conditions in the living body. Currently, in order to overcome the above problem, functionalized liposomes have become a very promising strategy. In this paper, binding strategies of liposomes with four main functional elements, namely nucleic acids, antibodies, peptides, and stimuli-responsive motif have been summarized for the first time. In addition, based on the construction characteristics of functionalized liposomes, such as drug-carrying, targeting, long-circulating, and stimulus-responsive properties, a comprehensive overview of their features and respective research progress are presented. Finally, the paper critically presents the limitations of these functionalized liposomes in the current applications and also prospectively suggests the future development directions, aiming to accelerate realization of their industrialization.

Euglena's atypical respiratory chain adapts to the discoidal cristae and flexible metabolism.

Euglena gracilis, a model organism of the eukaryotic supergroup Discoba harbouring also clinically important parasitic species, possesses diverse metabolic strategies and an atypical electron transport chain. While structures of the electron transport chain complexes and supercomplexes of most other eukaryotic clades have been reported, no similar structure is currently available for Discoba, limiting the understandings of its core metabolism and leaving a gap in the evolutionary tree of eukaryotic bioenergetics. Here, we report high-resolution cryo-EM structures of Euglena's respirasome I + III2 + IV and supercomplex III2 + IV2. A previously unreported fatty acid synthesis domain locates on the tip of complex I's peripheral arm, providing a clear picture of its atypical subunit composition identified previously. Individual complexes are re-arranged in the respirasome to adapt to the non-uniform membrane curvature of the discoidal cristae. Furthermore, Euglena's conformationally rigid complex I is deactivated by restricting ubiquinone's access to its substrate tunnel. Our findings provide structural insights for therapeutic developments against euglenozoan parasite infections.

Increase of stress resistance in Lactococcus lactis via a novel food-grade vector expressing a shsp gene from Streptococcus thermophilus

The effects of the expression of a small heat shock protein (shsp) gene from Streptococcus thermophilus on stress resistance in Lactococcus lactis under different environmental stresses were investigated in this study. pMG36e-shsp, an expression vector, was first constructed by inserting a shsp open reading frame (ORF) cloned from S. thermophilus strain St-QC into pMG36e. Then, a food-grade expression vector, pMG-shsp, was generated by deleting the erythromycin resistance gene from pMG36e-shsp. The transformation rate of pMG-shsp was comparable to that of pMG36e-shsp when each of these two vectors was introduced into L. lactis. These results demonstrated that the shsp ORF could successfully used as a food-grade selection marker in both pMG-shsp and pMG36e-shsp. Furthermore, the growth characteristics were almost the same between L. lactis ML23 transformants harboring pMG36e or pMG-shsp. The survival rate of L. lactis ML23 expressing the shsp ORF were increased to 0.032%, 0.006%, 0.0027%, 0.03%, and 0.16% under the following environmental stresses: heat, acid, ethanol, bile salt and H2O2, respectively. These results indicated that the expression of the shsp gene in the food-grade vector pMG-shsp conferred resistance to environmental stresses without affecting the growth characteristics of L. lactis ML23.