Unveiling the Effect of Myo-inositol on Primitive Cell Models Derived from Fatty Acid

Early forms of life on Earth were most likely not complex. Simple non-living molecules may have formed aggregates, orunderwent spontaneous complex organic reactions resulting in build-up of molecular complexity leading to origin of life. Protocell (hypothetical first live cell) models based on fatty acid self-assemblies have been used in many experiments. Sugars, amino acids and nucleic acids are the backbone of any living creature. Myo-inositol (InOH), is structurally similar to pyranose form of d-glucose. InOH not only has higher stability than simple sugars, but also not easily degraded under extreme conditions. Therefore, InOH would have persisted in the hostile environment of early Earth. Here, our objective is to study the effect of varying concentrations of InOH, a prebiotic sugar-like biomolecule, on the self-assemblies derived from oleic acid using solvation dynamics as a major experimental tool. We have demonstrated that InOH does indeed perturb the membrane of oleic acid/oleate vesicles, which is characterized by more negative zeta potential of vesicles, and faster solvation dynamics of the solvation probe C153. Overall, our results provide significant insight towards understanding the role of carbohydrate osmolytes in relation to protocell models.

Liposomal Nω-hydroxy-l-norarginine, a proof-of-concept: Arginase inhibitors can be incorporated in liposomes while retaining their therapeutic activity ex vivo

Cancer immunotherapy has evolved significantly over the last decade, with therapeutics targeting the adaptive immune system showing exciting effects in clinics. Yet, the modulation of the innate immune system, particularly the tumor-associated innate immune cells which are an integral part of immune responses in cancer, remains less understood. The arginase 1 (Arg1) pathway is a pivotal metabolic pathway that tumor-associated innate immune cells exploit to create an immunosuppressive tumor microenvironment, leading to the evasion of immune surveillance. The inhibition of Arg1 presents a therapeutic opportunity to reverse this immunosuppression, and Nω‑hydroxy-l-norarginine (nor-NOHA) has emerged as a potent arginase inhibitor with promising in vivo efficacy. However, the rapid systemic clearance of nor-NOHA poses a significant challenge for its therapeutic application. This study pioneers the encapsulation of nor-NOHA in liposomes, aiming to enhance its bioavailability and prolong its inhibitory activity against Arg1. Historically, the extensive interaction between innate immune cells and nanoparticles has been one of the biggest drawbacks in nanomedicine. Here we seek to utilize this effect and deliver liposomal nor-NOHA to the arginase 1 expressing innate immune cells. We systematically investigated the effect of lipid composition, acyl chain length, manufacturing and loading methodology on the encapsulation efficiency (EE%) and release profile of nor-NOHA. Our results indicate that while the manufacturing method and lipid acyl chain length do not significantly impact EE%, they crucially influence the release kinetics of nor-NOHA, with longer acyl chains demonstrating a more sustained release of nor-NOHA from liposomes enabling continuous inhibition of Arg1. Our findings suggest that liposomal nor-NOHA retains its functional inhibitory activity and could offer improved pharmacokinetic properties, making it a compelling base for iterations for further innovative cancer immunotherapeutic strategies in preclinical and clinical evaluations.

Liquid fertilizers produced by microwave-assisted acid hydrolysis of livestock and poultry wastes and their effects on hot pepper cultivation

Liquid fertilizers (LFs) produced by microwave-assisted acid hydrolysis of livestock and poultry wastes were applied to potted hot pepper (Capsicum annuum L.) to evaluate their potential to be used as amino acid LFs. A preliminary experiment was conducted to determine the optimum acid-hydrolysis conditions for producing LFs from a mixture of pig hair and faeces (P) and another mixture of chicken feathers and faeces (C). Two LFs were produced under the optimum acid-hydrolysis conditions (acidification by sulphuric acid (7.5 mol L-1) in a microwave (200 W) for 90 minutes), and a commercial amino acid LF (Guo Guang (GG)) was used for comparison. P, C and GG fertilizers were tested in potted hot pepper cultivation at two doses, whereas no fertilizer application served as the control (CK). P and C fertilizers significantly increased the fruit yield compared with GG fertilizer, particularly at the higher dose. Moreover, the treatments improved the fruit vitamin C and soluble sugar contents in the order of C > P > GG compared with CK. These results could be attributed to more types of amino acids in C fertilizer than in P and GG fertilizers. The results also indicated that the prepared fertilizers could significantly increase the shoot and root dry weight, soil available nitrogen and phosphorus contents and nitrogen, phosphorus, and potassium (NPK) uptake by plants compared with CK. In conclusion, microwave-assisted acid hydrolysis could effectively convert unusable wastes into valuable fertilizers comparable or even superior to commercial fertilizers.

Chain-Length Dependence of Peptide-Lipid Bilayer Interaction Strength and Binding Kinetics: A Combined Theoretical and Experimental Approach

Physical interactions between polypeptide chains and lipid membranes underlie critical cellular processes. Yet, despite fundamental importance, key mechanistic aspects of these interactions remain elusive. Bulk experiments have revealed a linear relationship between free energy and peptide chain length in a model system, but does this linearity extend to the interaction strength and to the kinetics of lipid binding? To address these questions, we utilized a combination of coarse-grained molecular dynamics (CG MD) simulations, analytical modeling, and atomic force microscopy (AFM)-based single molecule force spectroscopy. Following previous bulk experiments, we focused on interactions between short hydrophobic peptides (WLn, n = 1, ..., 5) with 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC) bilayers, a simple system that probes peptide primary structure effects. Potentials of mean force extracted from CG MD recapitulated the linearity of free energy with the chain length. Simulation results were quantitatively connected to bulk biochemical experiments via a single scaling factor of order unity, corroborating the methodology. Additionally, CG MD revealed an increase in the distance to the transition state, a result that weakens the dependence of the dissociation force on the peptide chain length. AFM experiments elucidated rupture force distributions and, through modeling, intrinsic dissociation rates. Taken together, the analysis indicates a rupture force plateau in the WLn-POPC system, suggesting that the final rupture event involves the last 2 or 3 residues. In contrast, the linear dependence on chain length was preserved in the intrinsic dissociation rate. This study advances the understanding of peptide-lipid interactions and provides potentially useful insights for the design of peptides with tailored membrane-interacting properties.

Long-Term Stable Liposome Modified by PEG-Lipid in Natural Seawater

This paper describes the stabilization of liposomes using a PEGylated lipid, N-(methylpolyoxyethylene oxycarbonyl)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine sodium salt (DSPE-PEGs), and the evaluation of the survival rate in natural seawater for future environmental applications. Liposomes in natural seawater were first monitored by confocal microscopy, and the stability was compared among different lengths and the introduction ratio of DSPE-PEGs. The survival rate increased with an increase in the PEG ratio. In addition, the survival rate in different cationic solutions (Na+, K+, Mg2+, and Ca2+ solutions) was studied to estimate the effects of the DSPE-PEG introduction. We propose that these variations in liposome stability are due to the cations, specifically the interaction between the poly(ethylene glycol) (PEG) chains and divalent ions, which contribute to making it difficult for cations to access the lipid membrane. Our studies provide insights into the use of PEG lipids and may offer a promising approach to the fabrication of liposomal molecular robots using different natural environments.

Effect of Lipid Corona on Phenylalanine-Functionalized Gold Nanoparticles to Develop Stable and Corona-Free Systems

Conventional gold nanoparticles (Au NPs) have many limitations, such as aggregation and subsequent precipitation in the medium of high ionic strength and protein molecules. Furthermore, when exposed to biological fluids, nanoparticles form a protein corona, which controls different biological processes such as the circulation lifetime, drug release profile, biodistribution, and in vivo cellular distribution. These limitations reduce the functionality of Au NPs in targeted delivery, bioimaging, gene delivery, drug delivery, and other biomedical applications. To circumvent these problems, there are numerous attempts to design corona-free and stable nanoparticles. Here, we report for the first time that lipid corona (coating of lipid) formation on phenylalanine-functionalized Au NPs (AuPhe NPs) imparts excellent stability against the high ionic strength of bivalent metal ions, amino acids, and proteins of different charges as compared to bare nanoparticles. Moreover, this work is focused on the ability of lipid corona formation on AuPhe NPs to prevent protein adsorption in the presence of cell culture medium (CCM), oppositely charged protein (e.g., histone 3), and human serum albumin (HSA). The results demonstrate that the lipid corona successfully protects the AuPhe NPs from protein adsorption, leading to the development of corona-free character. This unique achievement has profound implications for enhancing the biomedical utility and safety of these nanoparticles.

Interactions between Lipid Vesicle Membranes and Single Amino Acid Fibrils: Probable Origin of Specific Neurological Disorders

Amyloid fibrils are known to be responsible for several neurological disorders, like Alzheimer's disease (AD), Parkinson's disease (PD), etc. For decades, mostly proteins and peptide-based amyloid fibrils have been focused on, and the topic has acknowledged the rise, development, understanding of, and controversy, as well. However, the single amino acid based amyloid fibrils, responsible for several disorders, such as phenylketonuria, tyrosenimia type II, hypermethioninemia, etc., have gotten scientific attention lately. To understand the molecular level pathogenesis of such disorders originated due to the accumulation of single amino acid-based amyloid fibrils, interaction of these fibrils with phospholipid vesicle membranes is found to be an excellent cell-free in vitro setup. Based on such an in vitro setup, these fibrils show a generic mechanism of membrane insertion driven by electrostatic and hydrophobic effects inside the membrane that reduces the integral rigidity of the membrane. Alteration of such fundamental properties of the membrane, therefore, might be referred to as one of the prime pathological factors for the development of these neurological disorders. Hence, such interactions must be investigated in cellular and intracellular compartments to design suitable therapeutic modulators against fibrils.

Phosphoglycerate kinase (PGK) 1 succinylation modulates epileptic seizures and the blood-brain barrier

Epilepsy is the most common chronic disorder in the nervous system, mainly characterized by recurrent, periodic, unpredictable seizures. Post-translational modifications (PTMs) are important protein functional regulators that regulate various physiological and pathological processes. It is significant for cell activity, stability, protein folding, and localization. Phosphoglycerate kinase (PGK) 1 has traditionally been studied as an important adenosine triphosphate (ATP)-generating enzyme of the glycolytic pathway. PGK1 catalyzes the reversible transfer of a phosphoryl group from 1, 3-bisphosphoglycerate (1, 3-BPG) to ADP, producing 3-phosphoglycerate (3-PG) and ATP. In addition to cell metabolism regulation, PGK1 is involved in multiple biological activities, including angiogenesis, autophagy, and DNA repair. However, the exact role of PGK1 succinylation in epilepsy has not been thoroughly investigated. The expression of PGK1 succinylation was analyzed by Immunoprecipitation. Western blots were used to assess the expression of PGK1, angiostatin, and vascular endothelial growth factor (VEGF) in a rat model of lithium-pilocarpine-induced acute epilepsy. Behavioral experiments were performed in a rat model of lithium-pilocarpine-induced acute epilepsy. ELISA method was used to measure the level of S100β in serum brain biomarkers' integrity of the blood-brain barrier. The expression of the succinylation of PGK1 was decreased in a rat model of lithium-pilocarpine-induced acute epilepsy compared with the normal rats in the hippocampus. Interestingly, the lysine 15 (K15), and the arginine (R) variants of lentivirus increased the susceptibility in a rat model of lithium-pilocarpine-induced acute epilepsy, and the K15 the glutamate (E) variants, had the opposite effect. In addition, the succinylation of PGK1 at K15 affected the expression of PGK1 succinylation but not the expression of PGK1total protein. Furthermore, the study found that the succinylation of PGK1 at K15 may affect the level of angiostatin and VEGF in the hippocampus, which also affects the level of S100β in serum. In conclusion, the mutation of the K15 site of PGK1 may alter the expression of the succinylation of PGK1 and then affect the integrity of the blood-brain barrier through the angiostatin / VEGF pathway altering the activity of epilepsy, which may be one of the new mechanisms of treatment strategies.

Unveiling the functional epitopes of cobra venom cytotoxin by immunoinformatics and epitope-omic analyses

Approximate 70% of cobra venom is composed of cytotoxin (CTX), which is responsible for the dermonecrotic symptoms of cobra envenomation. However, CTX is generally low in immunogenicity, and the antivenom is ineffective in attenuating its in vivo toxicity. Furthermore, little is known about its epitope properties for empirical antivenom therapy. This study aimed to determine the epitope sequences of CTX using the immunoinformatic analyses and epitope-omics profiling. A conserved CTX was used in this study to determine its T-cell and B-cell epitope sequences using immunoinformatic tools and molecular docking simulation with different Human Leukocyte Antigens (HLAs). The potential T-cell and B-cell epitopes were 'KLVPLFY,' 'CPAGKNLCY,' 'MFMVSTPTK,' and 'DVCPKNSLL.' Molecular docking simulations disclosed that the HLA-B62 supertype exhibited the greatest binding affinity towards cobra venom cytotoxin. The namely L7, G18, K19, N20, M25, K33, V43, C44, K46, N47, and S48 of CTX exhibited prominent intermolecular interactions with HLA-B62. The multi-enzymatic-limited-digestion/liquid chromatography-mass spectrometry (MELD/LC-MS) also revealed three potential epitope sequences as 'LVPLFYK,' 'MFMVS,' and 'TVPVKR'. From different epitope mapping approaches, we concluded four potential epitope sites of CTX as 'KLVPLFYK', 'AGKNL', 'MFMVSTPKVPV' and 'DVCPKNSLL'. Site-directed mutagenesis of these epitopes confirmed their locations at the functional loops of CTX. These epitope sequences are crucial to CTX's structural folding and cytotoxicity. The results concluded the epitopes that resided within the functional loops constituted potential targets to fabricate synthetic epitopes for CTX-targeted antivenom production.

Amyloids Formed by Nonaromatic Amino Acid Methionine and Its Cross with Phenylalanine Significantly Affects Phospholipid Vesicle Membrane: An Insight into Hypermethioninemia Disorder

The incorrect metabolic breakdown of the nonaromatic amino acid methionine (Met) leads to the disorder called hypermethioninemia via an unknown mechanism. To understand the molecular level pathogenesis of this disorder, we prepared a DMPC lipid membrane, the mimicking setup of the cell membrane, and explored the effect of the millimolar level of Met on it. We found that Met forms toxic fibrillar aggregates that disrupt the rigidity of the membrane bilayer, and increases the dynamic response of water molecules surrounding the membrane as well as the heterogeneity of the membrane. Such aggregates strongly deform red blood cells. This opens the requirement to consider therapeutic antagonists either to resist or to inhibit the toxic amyloid aggregates against hypermethioninemia. Moreover, such disrupting effect on membrane bilayer and cytotoxicity along with deformation effect on RBC by the cross amyloids of Met and Phenylalanine (Phe) was found to be most virulent. This exclusive observation of the enhanced virulent effect of the cross amyloids is expected to be an informative asset to explain the coexistence of two amyloid disorders.

Quantitative insights into tightly and loosely bound water in hydration shells of amino acids

The hydration of amino acids closely correlates the hydration of peptides and proteins and is critical to their biological functions. However, complete and quantitative understanding about the hydration of amino acids is lacking. Here, tightly and loosely bound water of 20 zwitterionic amino acids are quantitatively distinguished and determined by Raman spectroscopy with multivariate curve resolution (Raman-MCR) and differential scanning calorimetry (DSC). The total hydration water obtained from Raman-MCR and the tightly bound water determined by DSC have certain relevance, but they do not exactly correspond. In particular, Pro, Arg and Lys exhibit larger number of tightly bound water molecules (4.02-6.59), showing a significant influence on the onset transition temperature and the melting enthalpy values of water molecules, which provides direct evidence for their unique functions associated with biological water. Asn, Ser, Thr, Met, His and Glu have a smaller number of tightly bound water molecules (0.30-1.31), whilst the other remaining 11 amino acids only contain loosely bound water molecules. Four exceptional amino acids Ile, Leu, Phe and Val show fewer tightly bound water molecules but a higher number of loosely bound water molecules. As for the hydration shell structure, most amino acids except Pro and Trp enhance tetrahedral water structure and H-bonds relative to pure water and at least 1.9% of the hydration water molecules associated with the amino acids show non-hydrogen-bonded OH defects. This work combines two effective experimental techniques to reveal the hydration water structure and quantitatively analyze two kinds of bound water molecules of 20 amino acids.

Amino acids change solute affinity for lipid bilayers

Time-resolved fluorescence and differential scanning calorimetry (DSC) were used to examine how two amino acids, L-phenylalanine (L-PA) and N-acetyl-DL-tryptophan (NAT), affect the temperature-dependent membrane affinity of two structurally similar coumarin solutes for 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) vesicles. The 7-aminocoumarin solutes, coumarin 151 (C151) and coumarin 152 (C152), differ in their substitution at amine position-C151 is a primary amine, and C152 is a tertiary amine-and both solutes show different tendencies to associate with lipid bilayers consistent with differences in their respective log-P-values. Adding L-PA to the DPPC vesicle solution did not change C151's propensity to remain freely solvated in aqueous solution, but C152 showed a greater tendency to partition into the hydrophobic bilayer interior at temperatures below DPPC's gel-liquid crystalline transition temperature (Tgel-lc). This finding is consistent with L-PA's ability to enhance membrane permeability by disrupting chain-chain interactions. Adding NAT to DPPC-vesicle-containing solutions changed C151 and C152 affinity for the DPPC membranes in unexpected ways. DSC data show that NAT interacts strongly with the lipid bilayer, lowering Tgel-lc by up to 2°C at concentrations of 10 mM. These effects disappear when either C151 or C152 is added to solution at concentrations below 10 μM, and Tgel-lc returns to a value consistent with unperturbed DPPC bilayers. Together with DSC results, fluorescence data imply that NAT promotes coumarin adsorption to the vesicle bilayer surface. NAT's effects diminish above Tgel-lc and imply that unlike L-PA, NAT does not penetrate into the bilayer but instead remains adsorbed to the bilayer's exterior. Taken in their entirety, these discoveries suggest that amino acids-and by inference, polypeptides and proteins-change solute affinity for lipid bilayers with specific effects that depend on individualized amino-acid-lipid-bilayer interactions.

A Comparative Study on DMSO-Induced Modulation of the Structural and Dynamical Properties of Model Bilayer Membranes

Modulating the structures and properties of biomembranes via permeation of small amphiphilic molecules is immensely important, having diverse applications in cell biology, biotechnology, and pharmaceuticals, because their physiochemical and biological interactions lead to new pathways for transdermal drug delivery and administration. In this work, we have elucidated the role of dimethyl sulfoxide (DMSO), broadly used as a penetration-enhancing agent and cryoprotective agent on model lipid membranes, using a combination of fluorescence microscopy and time-resolved fluorescence spectroscopy. Spatially resolved fluorescence lifetime imaging microscopy (FLIM) has been employed to unravel how the fluidity of the DMSO-induced bilayer regulates the structural alteration of the vesicles. Moreover, we have also shown that the dehydration effect of DMSO leads to weakening of the hydrogen bond between lipid headgroups and water molecules and results in faster solvation dynamics as demonstrated by femtosecond time-resolved fluorescence spectroscopy. It has been gleaned that the water dynamics becomes faster because bilayer rigidity decreases in the presence of DMSO, which is also supported by time-resolved rotational anisotropy measurements. The enhanced diffusivity and increased membrane fluidity in the presence of DMSO are further ratified at the single-molecule level through fluorescence correlation spectroscopy (FCS) measurements. Our results indicate that while the presence of DMSO significantly affects the 1,2-dimyristoyl-rac-glycero-3-phosphocholine (DMPC) and 1,2-dipalmitoyl-rac-glycero-3-phosphatidylcholine (DPPC) bilayers, it has a weak effect on 1,2-dimyristoyl-sn-glycero-3-phospho-rac-glycerol (DMPG) vesicles, which might explain the preferential interaction of DMSO with the positively charged choline group present in DMPC and DPPC vesicles. The experimental findings have also been further verified with molecular dynamics simulation studies. Moreover, it has been observed that DMSO is likely to have a differential effect on heterogeneous bilayer membranes depending on the structure and composition of their headgroups. Our results illuminate the importance of probing the lipid structure and composition of cellular membranes in determining the effects of cryoprotective agents.

Discriminatory Interaction Behavior of Lipid Vesicles toward Diversely Emissive Carbon Dots Synthesized from Ortho, Meta, and Para Isomeric Carbon Precursors

Photoluminescent carbon dots (C-dots) are widely used for bioimaging techniques to study different cellular processes. However, biocompatibility of C-dots is crucial because the wrong selection of C-dots may lead to an adverse effect on a particular cellular process. Herein, we investigate the interaction of zwitterionic lipid vesicles with photoluminescent C-dots derived from different isomeric (ortho, meta, and para) precursors of phenylenediamine (PDA) by spectroscopic and microscopic imaging techniques as well as dynamic light scattering methods. The study reveals that interaction of lipid vesicles with C-dots is highly dependent on the properties of the isomeric precursors. We find that vesicles retain their morphology upon interaction with ortho C-dots (oCD). The microscopic images reveal that oCD are selectively embedded in the lipid vesicles and can effectively be used for imaging purpose. On the contrary, meta and para C-dots (mCD and pCD) being located on the interfacial region induce aggregation in the vesicles. We explain the observation in terms of the location of the C-dots on the lipid vesicles, their electrostatic attraction at the vesicle interface, possible cross-linking with other vesicles and different hydration features of the isomeric precursors of the C-dots. The study may be helpful in understanding the interactions and attachment processes of C-dots at the interface of biological membranes.