Enhancing extraction efficiency of carpaine in L. leaves: coupling acid-base extraction with surfactant-assisted micro-flotation.

Carpaine, a major alkaloid in papaya leaves, has considerable cardiovascular benefits alongside its notable effects on muscle relaxation when utilized in medicine. In this study, the coupling of acid-base extraction and flotation was developed to completely remove the use of toxic solvents. This method entails the extraction of carpaine from L.

Investigating the effects of ultrafine bubbles on bacterial growth.

Several previous studies have considered ultrafine bubbles as a potential research target because their properties can be applied in many different research areas. In particular, the interaction between UFBs and microorganisms has always been one of the aspects that receives much attention due to the high difficulty in controlling a living system. The properties of UFBs, as mobile air-water interfaces, are greatly determined by their gas cores which play a critical role in regulating microbial growth.

Review on the Significant Interactions between Ultrafine Gas Bubbles and Biological Systems.

Having sizes comparable with living cells and high abundance, ultrafine bubbles (UBs) are prone to inevitable interactions with different types of cells and facilitate alterations in physiological properties. The interactions of four typical cell types (e.g.

Crucial Role of Surfactants in Improving the Extraction Efficiency of β-Amyrin from Using Ultrasound-Assisted Extraction Coupled with Gas Bubble Flotation.

Ultrasound-assisted extraction coupled with gas bubble flotation was developed as a green method for extracting β-amyrin from. The solvent system was water:ethanol (9:1). To improve the adsorption of β-amyrin onto the air/liquid interface during flotation, surfactants were employed; however, the positive effect was only observed with cationic surfactants.

Hydrophobizing cellulose surfaces via catalyzed transesterification reaction using soybean oil and starch.

Biodegradable modified natural polymers have great potential in curbing the threat of plastic pollution, but are still uncompetitive to petrochemical-based plastic. In this study, starch was hydrophobized by treating starch-dimethyl sulfoxide solutions with soybean oil at high temperature in the presence of sodium carbonate, then spray-coated on paper. The modified starch was evaluated by Fourier-transform infrared spectroscopy analysis and contact angle value measurement of coated paper.

Effects of Ultrafine Bubbles on Gram-Negative Bacteria: Inhibition or Selection?

Ultrafine bubbles exist in all liquids and are naturally stable. As their properties are not entirely known, it is unclear how they impact the surrounding solution and comparable-sized particles within it. It is essential to further investigate the properties of ultrafine bubbles in order to expand their industrial application.

New Evidence of Head-to-Tail Complex Formation of SDS-DOH Mixtures Adsorbed at the Air-Water Interface as Revealed by Vibrational Sum Frequency Generation Spectroscopy and Isotope Labelling.

Details about the molecular structures of surfactant mixtures adsorbed at the air-water interface have been controversial. Using sum frequency generation vibrational spectroscopy (SFG) and isotope labeling, we show here for the first time that mixtures of dodecanol (DOH) and sodium dodecyl sulfate (SDS) adsorb at the air-water interface with the formation of a head-to-tail complex. We observed this complex formation to occur first in the aqueous subphase, followed by complex adsorption onto the interface.

Combined Sum Frequency Generation and Thin Liquid Film Study of the Specific Effect of Monovalent Cations on the Interfacial Water Structure.

Some salts have been recently shown to decrease the sum frequency generation (SFG) intensity of the hydrogen-bonded water molecules, but a quantitative explanation is still awaited. Here, we report a similar trend for the chloride salts of monovalent cations, that is, LiCl, NaCl, and CsCl, at low concentrations. Specifically, we revealed not only the specific adsorption of cations at the water surface but also the concentration-dependent effect of ions on the SFG response of the interfacial water molecules.

In Situ Investigation of Peptide-Lipid Interaction Between PAP248-286 and Model Cell Membranes.

Sum frequency generation vibrational spectroscopy (SFG) was utilized to investigate the interaction between PAP248-286 and the two lipid bilayer systems. The present study also provides spectroscopic evidence to confirm that, although PAP248-286 is unable to penetrate into the hydrophobic core of the lipid bilayers, it is capable of interacting more intimately with the fluid-phase POPG/POPC than with the gel-phase DPPG/DPPC lipid bilayer. The helical structure content of lipid-bound PAP248-286 was also observed to be high, in contrast to the results previously reported using nuclear magnetic resonance (NMR).

A sum-frequency generation spectroscopic study of the Gibbs analysis paradox: monolayer or sub-monolayer adsorption?

The Gibbs adsorption isotherm (GAI) has been considered as the foundation of surfactant adsorption studies for over a century; however, its application in determining the limiting surface excess has recently been intensively discussed, with contradictory experimental evidence either supporting or refuting the theory. The available arguments are based on monolayer adsorption models. In this paper, we experimentally and intellectually propose and validate the contribution of sub-monolayer adsorption to the GAI paradox.

Suppressing interfacial water signals to assist the peak assignment of the N⁺-H stretching mode in sum frequency generation vibrational spectroscopy.

Amines are one of the common functional groups of interest due to their abundant presence in natural proteins, surfactants and other chemicals. However, their accurate spectral assignment of vibrational modes, critical to interpreting SFG signals for characterizing various bio-interfaces such as protein-membrane interaction and surfactant adsorption, still remains elusive. Herein we present a systematic study to identify and justify the correct peak assignment of the N(+)-H stretching mode at the air-water interface.

An electronically enhanced chiral sum frequency generation vibrational spectroscopy study of lipid-bound cytochrome c.

Electronically enhanced chiral SFG spectroscopy was employed to study the lipid bound cyt c in situ. It was directly observed that upon interacting with anionic phospholipids, the amino acid residues around the heme adopted the β-sheet conformation. In addition, the orientation of this newly formed β-sheet structure was found to be sensitive to the bulk pH.

Interactions between halide anions and interfacial water molecules in relation to the Jones-Ray effect.

The Jones-Ray effect is shown to be governed by a different mechanism to enhanced anion adsorption. Halide ions at sub-molar concentrations are not exposed to the vapour phase; instead their first-solvating shell intimately interacts with the outmost water layer. Our novel proposal opens challenges for predicting related interfacial phenomena consistently.

In situ investigation of halide co-ion effects on SDS adsorption at air-water interfaces.

Co-ions are believed to have a negligible effect on surfactant adsorption, but we show here that they can significantly affect the surfactant adsorption at the air-water interface. Sum frequency generation vibrational spectroscopy (SFG) was employed to examine the effects of three halides (Cl(-), Br(-) and I(-)) on the adsorption of an anionic surfactant, sodium dodecyl sulphate (SDS), at the air-water interface. The SFG spectral features of both the interfacial water molecules and the C-H vibrations of the adsorbed surfactant alkyl chains were analysed to characterize the surfactant adsorption.

Probing the spontaneous membrane insertion of a tail-anchored membrane protein by sum frequency generation spectroscopy.

In addition to providing a semipermeable barrier that protects a cell from harmful stimuli, lipid membranes occupy a central role in hosting a variety of biological processes, including cellular communications and membrane protein functions. Most importantly, protein-membrane interactions are implicated in a variety of diseases and therefore many analytical techniques were developed to study the basis of these interactions and their influence on the molecular architecture of the cell membrane. In this study, sum frequency generation (SFG) vibrational spectroscopy is used to investigate the spontaneous membrane insertion process of cytochrome b(5) and its mutants.

Orientation determination of interfacial beta-sheet structures in situ.

Structural information such as orientations of interfacial proteins and peptides is important for understanding properties and functions of such biological molecules, which play crucial roles in biological applications and processes such as antimicrobial selectivity, membrane protein activity, biocompatibility, and biosensing performance. The alpha-helical and beta-sheet structures are the most widely encountered secondary structures in peptides and proteins. In this paper, for the first time, a method to quantify the orientation of the interfacial beta-sheet structure using a combined attenuated total reflectance Fourier transformation infrared spectroscopic (ATR-FTIR) and sum frequency generation (SFG) vibrational spectroscopic study was developed.

Interactions of alamethicin with model cell membranes investigated using sum frequency generation vibrational spectroscopy in real time in situ.

Structures of membrane-associated peptides and molecular interactions between peptides and cell membrane bilayers govern biological functions of these peptides. Sum frequency generation (SFG) vibrational spectroscopy has been demonstrated to be a powerful technique to study such structures and interactions at the molecular level. In this research, SFG has been applied, supplemented by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), to characterize the interactions between alamethicin (a model for larger channel proteins) and different lipid bilayers in the absence of membrane potential.

Orientation difference of chemically immobilized and physically adsorbed biological molecules on polymers detected at the solid/liquid interfaces in situ.

A surface sensitive second order nonlinear optical technique, sum frequency generation vibrational spectroscopy, was applied to study peptide orientation on polymer surfaces, supplemented by a linear vibrational spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy. Using the antimicrobial peptide Cecropin P1 as a model system, we have quantitatively demonstrated that chemically immobilized peptides on polymers adopt a more ordered orientation than less tightly bound physically adsorbed peptides. These differences were also observed in different chemical environments, for example, air versus water.

Molecular interactions between magainin 2 and model membranes in situ.

In this paper, we investigated the molecular interactions of magainin 2 with model cell membranes using sum frequency generation (SFG) vibrational spectroscopy and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). Symmetric 1-palmitoyl-2-oleoyl-sn-glycero-3-[Phospho-rac-(1-glycerol)] (POPG) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayers, which model the bacterial and mammalian cell membranes, respectively, were used in the studies. It was observed by SFG that magainin 2 orients relatively parallel to the POPG lipid bilayer surface at low solution concentrations, around 200 nM.

Orientation determination of protein helical secondary structures using linear and nonlinear vibrational spectroscopy.

In this paper, we systematically presented the orientation determination of protein helical secondary structures using vibrational spectroscopic methods, particularly, nonlinear sum frequency generation (SFG) vibrational spectroscopy, along with linear vibrational spectroscopic techniques such as infrared spectroscopy and Raman scattering. SFG amide I signals can be collected using different polarization combinations of the input laser beams and output signal beam to measure the second-order nonlinear optical susceptibility components of the helical amide I modes, which are related to their molecular hyperpolarizability elements through the orientation distribution of these helices. The molecular hyperpolarizability elements of amide I modes of a helix can be calculated based on the infrared transition dipole moment and Raman polarizability tensor of the helix; these quantities are determined by using the bond additivity model to sum over the individual infrared transition dipole moments and Raman polarizability tensors, respectively, of the peptide units (or the amino acid residues).

In situ molecular level studies on membrane related peptides and proteins in real time using sum frequency generation vibrational spectroscopy.

Sum frequency generation (SFG) vibrational spectroscopy has been demonstrated to be a powerful technique to study the molecular structures of surfaces and interfaces in different chemical environments. This review summarizes recent SFG studies on hybrid bilayer membranes and substrate-supported lipid monolayers and bilayers, the interaction between peptides/proteins and lipid monolayers/bilayers, and bilayer perturbation induced by peptides/proteins. To demonstrate the ability of SFG to determine the orientations of various secondary structures, studies on the interactions between different peptides/proteins (melittin, G proteins, alamethicin, and tachyplesin I) and lipid bilayers are discussed.