Interactions of very long-chain saturated fatty acids with serum albumin

Self-assembled nanonization of fatty acid-conjugated vaccine antigen for enhanced thermal stability

The aim of this study was to evaluate the enhanced thermal stability and physicochemical properties of fattigated vaccine antigens. High molecular weight influenza hemagglutinin (Heg) was used as a model antigen because of low heat stability requiring cold chamber. Heg was conjugated with long-chain oleic acid (C18) and short-chain 3-decenoic acid (C10) to prepare fattigated Heg. Circular dichroism analysis revealed no significant changes in the three-dimensional structure post-conjugation. In the liquid state, the fattigated Heg was self-assembled into nanoparticles (NPs) due to its amphiphilic nature, with sizes of 136.27 ± 12.78 nm for oleic acid-conjugated Heg (HOC) and 88.73 ± 3.27 nm for 3-decenoic acid-conjugated Heg (HDC). Accelerated thermal stability studies at 60 °C for 7 days demonstrated that fattigated Heg exhibited higher thermal stability than Heg in various liquid or solid states. The longer-chained HOC showed better thermal stability than HDC in the liquid state, attributed to increased hydrophobic interactions during self-assembly. In bio-mimicking liquid states at 37 °C, HOC exhibited higher thermal stability than Heg. Furthermore, solid-state HOC with cryoprotectants (trehalose, mannitol, and Tween® 80) had significantly increased thermal stability due to reduced exposure of protein surface area via nanonization behavior. The current fattigation platform could be a promising strategy for developing thermostable nano vaccines of heat-labile vaccine antigens.

Nano-Bio Interactions between DNA Nanocages and Human Serum Albumin

DNA nanostructures have emerged as promising nanomedical tools due to their biocompatibility and tunable behavior. Recent work has shown that DNA nanocages decorated with organic dendrimers strongly bind human serum albumin (HSA), yet the dynamic structures of these complexes remain uncharacterized. This theoretical and computational investigation elucidates the fuzzy interactions between dendritically functionalized cubic DNA nanocages and HSA. The dendrimer-HSA interactions occur via nonspecific binding with the protein thermodynamically and kinetically free to cross the open faces of the cubic scaffold. However, the rigidity of the DNA scaffold prevents the binding energetics from scaling with the number of dendrimers. These discoveries not only provide a useful framework by which to model general interactions of DNA nanostructures complexed with serum proteins but also give valuable molecular insight into the design of next-generation DNA nanomedicines.

Molecular analysis and therapeutic applications of human serum albumin-fatty acid interactions

Human serum albumin (hSA) is the major carrier protein for fatty acids (FAs) in plasma. Its ability to bind multiple FA moieties with moderate to high affinity has inspired the use of FA conjugation as a safe and natural platform to generate long-lasting therapeutics with enhanced pharmacokinetic properties and superior efficacy. In this frame, the choice of the FA is crucial and a comprehensive elucidation of the molecular interactions of FAs with hSA cannot be left out of consideration. To this intent, we report here a comparative analysis of the binding mode of different FA moieties with hSA. The choice among different albumin-binding FAs and how this influence the pharmacokinetics properties of a broad spectrum of therapeutic molecules will be discussed including a critical description of some clinically relevant FA conjugated therapeutics.

Deciphering albumin-directed drug delivery by imaging

Albumin is the most abundant plasma protein, exhibits extended circulating half-life, and its properties have long been exploited for diagnostics and therapies. Many drugs intrinsically bind albumin or have been designed to do so, yet questions remain about true rate limiting factors that govern albumin-based transport and their pharmacological impacts, particularly in advanced solid cancers. Imaging techniques have been central to quantifying - at a molecular and single-cell level - the impact of mechanisms such as phagocytic immune cell signaling, FcRn-mediated recycling, oncogene-driven macropinocytosis, and albumin-drug interactions on spatial albumin deposition and related pharmacology. Macroscopic imaging of albumin-binding probes quantifies vessel structure, permeability, and supports efficiently targeted molecular imaging. Albumin-based imaging in patients and animal disease models thus offers a strategy to understand mechanisms, guide drug development and personalize treatments.

Bioactive peptides of whey: obtaining, activity, mechanism of action, and further applications

Bioactive peptides derived from diverse food proteins have been part of diverse investigations. Whey is a rich source of proteins and components related to biological activity. It is known that proteins have effects that promote health benefits. Peptides derived from whey proteins are currently widely studied. These bioactive peptides are amino acid sequences that are encrypted within the first structure of proteins, which required hydrolysis for their release. The hydrolysis could be through in vitro or in vivo enzymatic digestion and using microorganisms in fermented systems. The biological activities associated with bio-peptides include immunomodulatory properties, antibacterial, antihypertensive, antioxidant and opioid, etc. These functions are related to general conditions of health or reduced risk of certain chronic illnesses. To determine the suitability of these peptides/ingredients for applications in food technology, clinical studies are required to evaluate their bioavailability, health claims, and safety of them. This review aimed to describe the biological importance of whey proteins according to the incidence in human health, their role as bioactive peptides source, describing methods, and obtaining technics. In addition, the paper exposes biochemical mechanisms during the activity exerted by biopeptides of whey, and their application trends.

Refolding of denatured gold nanoparticles-conjugated bovine serum albumin through formation of catanions between gemini surfactant and sodium dodecyl sulphate

The present work elucidates binding interactions of sodium dodecyl sulphate (SDS) with the conjugated gold nanoparticles (AuNPs)-bovine serum albumin (BSA), unfolded by each of two gemini surfactants, 1,4-bis(dodecyl-N,N-dimethylammonium bromide)-butane (12-4-12,2Br-) or 1,8-bis(dodecyl-N,N-dimethylammonium bromide)-octane (12-8-12,2Br-). Initially, at a low concentration of SDS there is a relaxation of bioconjugates from their compressed form due to the formation of catanions between SDS and gemini surfactants. On moving towards higher concentrations of SDS, these relaxed unfolded bioconjugates renature by removal of residual bound gemini surfactants. Mixed assemblies of SDS and gemini surfactants formed during refolding of bioconjugates are characterized by DLS and FESEM measurements. A step-by-step process of refolding observed for these denatured protein bioconjugates is exactly the inverse of their unfolding phenomenon. Parameters concerning nanometal surface energy transfer (NSET) and Förster's resonance energy transfer (FRET) phenomenon were employed to develop a binding isotherm. Moreover, there remains an inverse relationship between α-helix and β-turns of bioconjugates during the refolding process. Significantly, in the presence of 12-8-12,2Br-, SDS induces more refolding as compared to that for 12-4-12,2Br-. Bioconjugation shows an effect on the secondary structures of refolded BSA, which has been explored in detail through various studies such as Fourier transform infrared spectroscopy, fluorescence, and circular dichroism (CD). Therefore, this approach vividly describes the refolding of denatured bioconjugates, exploring structural information regarding various catanions formed during the process that would help in understanding distance-dependent optical biomolecular detection methodologies and physicochemical properties.

The Study of Protein-Cyclitol Interactions

Investigation of interactions between the target protein molecule and ligand allows for an understanding of the nature of the molecular recognition, functions, and biological activity of protein-ligand complexation. In the present work, non-specific interactions between a model protein (Bovine Serum Albumin) and four cyclitols were investigated. D-sorbitol and adonitol represent the group of linear-structure cyclitols, while shikimic acid and D-(-)-quinic acid have cyclic-structure molecules. Various analytical methods, including chromatographic analysis (HPLC-MS/MS), electrophoretic analysis (SDS-PAGE), spectroscopic analysis (spectrofluorimetry, Fourier transform infrared spectroscopy, and Raman spectroscopy), and isothermal titration calorimetry (ITC), were applied for the description of protein-cyclitol interactions. Additionally, computational calculations were performed to predict the possible binding places. Kinetic studies allowed us to clarify interaction mechanisms that may take place during BSA and cyclitol interaction. The results allow us, among other things, to evaluate the impact of the cyclitol's structure on the character of its interactions with the protein.

Bioactive compounds: Application of albumin nanocarriers as delivery systems

Enriched products with bioactive compounds (BCs) show the capacity to produce a wide range of possible health effects. Most BCs are essentially hydrophobic and sensitive to environmental factors; so, encapsulation becomes a strategy to solve these problems. Many globular proteins have the intrinsic ability to bind, protect, encapsulate, and introduce BCs into nutraceutical or pharmaceutical matrices. Among them, albumins as human serum albumin (HSA), bovine serum albumin (BSA), ovalbumin (OVA) and α-lactalbumin (ALA) are widely abundant, available, and applied in many industrial sectors, becoming promissory materials to encapsulate BCs. Therefore, this review focuses on researches about the main groups of natural origin BCs (namely phenolic compounds, lipids, vitamins, and carotenoids), the different types of nanostructures based on albumins to encapsulate them and the main fields of application for BCs-loaded albumin systems. In this context, phenolic compounds (catechins, quercetin, and chrysin) are the most extensively BCs studied and encapsulated in albumin-based nanocarriers. Other extensively studied subgroups are stilbenes and curcuminoids. Regarding lipids and vitamins; terpenes, carotenoids (β-carotene), and xanthophylls (astaxanthin) are the most considered. The main application areas of BCs are related to their antitumor, anti-inflammatory, and antioxidant properties. Finally, BSA is the most used albumin to produced BCs-loaded nanocarriers.

Very long-chain saturated fatty acids and diabetes and cardiovascular disease

PURPOSE OF REVIEW

In contrast to other saturated fatty acids, very long-chain saturated fatty acids (VLSFAs) have received limited attention The purpose of this review is to summarize the associations of VLSFAs, including arachidic acid, behenic acid, and lignoceric acid, with cardiovascular disease outcomes and type 2 diabetes; to discuss the findings implications; and to call for future studies of the VLSFAs.

RECENT FINDINGS

Increased levels of circulating VLSFAs have been found associated with lower risks of incident heart failure, atrial fibrillation, coronary heart disease, mortality, sudden cardiac arrest, type 2 diabetes, and with better aging. The VLSFA associations are paralleled by associations of plasma ceramide and sphingomyelin species carrying a VLSFA with lower risks of heart failure, atrial fibrillation, and mortality, suggesting VLSFAs affect the biological activity of ceramides and sphingomyelins thereby impacting health. For diabetes, there is no such parallel and the associations of VLSFAs with diabetes may be confounded or mediated by triglyceride and circulating palmitic acid, possible biomarkers of de novo lipogenesis.

SUMMARY

In many ways, the epidemiology has preceded our knowledge of VLSFAs biology. We hope this review will spur interest from the research community in further studying these potentially beneficial fatty acids.

Influence of bound dodecanoic acid on the reconstitution of albumin nanoparticles from a lyophilized state

The development of reference standards for nanoparticle sizing allows for cross laboratory studies and effective transfer of particle sizing methodology. To facilitate this, these reference standards must be stable upon long-term storage. Here, we examine factors that influence the properties of cross-linked albumin nanoparticles, fabricated with an ethanol desolvation method, when reconstituted from a lyophilized state. We demonstrate, with nanoparticle tracking analysis, no significant changes in mean particle diameter upon reconstitution of albumin nanoparticles fabricated with bovine serum albumin loaded with dodecanoic acid, when compared to nanoparticles fabricated with a fatty acid-free BSA. We attribute this stability to the modulation of nanoparticle charge-charge interactions at dodecanoic acid specific binding locations. Furthermore, we demonstrate this in a lyophilized state over six months when stored at − 80 °C. We also show that the reconstitution process is readily transferable between technicians and laboratories and further confirm our finding with dynamic light scattering analysis.

Tuning G-Quadruplex Nanostructures with Lipids. Towards Designing Hybrid Scaffolds for Oligonucleotide Delivery

Two G-quadruplex forming oligonucleotides [d(TG₄T)₄ and d(TG₆T)₄] were selected as two tetramolecular quadruplex nanostructures because of their demonstrated ability to be modified with hydrophobic molecules. This allowed us to synthesize two series of G-quadruplex conjugates that differed in the number of G-tetrads, as well as in the terminal position of the lipid modification. Both solution and solid-phase syntheses were carried out to yield the corresponding lipid oligonucleotide conjugates modified at their 3′- and 5′-termini, respectively. Biophysical studies confirmed that the presence of saturated alkyl chains with different lengths did not affect the G-quadruplex integrity, but increased the stability. Next, the G-quadruplex domain was added to an 18-mer antisense oligonucleotide. Gene silencing studies confirmed the ability of such G-rich oligonucleotides to facilitate the inhibition of target Renilla luciferase without showing signs of toxicity in tumor cell lines.

A review on neuropharmacological role of erucic acid: an omega-9 fatty acid from edible oils

Neurodegenerative diseases (ND) are characterised by loss of neurons in the brain and spinal cord. For the normal functioning of the brain, divers group of fatty acids in the form of glycerophospholipids, glycerol ether lipids, cerebrosides, sulfatides, and gangliosides are essential. They are present abundantly in the nervous system and are actively involved in both the development and maintenance of the nervous system. A dietary deficiency of essential fatty acid during development results in hypomyelination state which affects various neuronal functions. Several studies suggested that age remains the primary risk factor for almost all neurodegenerative disorders. The potential contribution of these fatty acids in the progression of neurodegenerative disorders is indispensable. Erucic acid an omega 9 fatty acid, which is obtained from edible oils has proven to cause myocardial lipidosis, heart lesions and hepatic steatosis in animals therefore, its content in edible oils is restricted to certain levels by regulatory agencies. However, erucic acid in the form of a mixture with oleic acid is often used as a dietary treatment for the management of adrenoleukodystrophy without any cardiotoxicity. Our literature search revealed that, erucic acid reported to enhance cognitive function, interact with peroxisome proliferator activated receptors (PPARs), inhibit elastase and thrombin. In this review first we have attempted to describe the relationship between fatty acids and neurodegeneration followed by a description on the pharmacology of erucic acid. The overall purpose of this review is to analyse toxic and beneficial neuropharmacological effects of erucic acid.

Photo-controlled delivery of very long chain fatty acids to cell membranes and modulation of membrane protein function

The biophysical properties and biological functions of membranes are highly dependent on lipid composition. Supplementing cellular membranes with very long chain fatty acids (vlcFAs) is notoriously difficult given the extreme insolubility of vlcFAs in aqueous solution. Herein, we report a solvent-free, photochemical approach to enrich target membranes with vlcFA. To prevent aggregation of vlcFA, we created light-sensitive micelles composed exclusively of poly-ethylene-glycol-nervonic acid amphiphiles (NA-PEG), which spontaneously disassemble in the presence of lipid bilayers. Once embedded within a membrane, UV light is used to cleave off PEG, leaving free nervonic acid (NA, i.e. FA24:1) in the target membrane. When applied to living cells, free NA was processed by the cell to generate various species of membrane and other lipids with incorporated vlcFAs. In this way, we were able to alter the membrane lipid composition of cellular membranes and modulate the enzymatic activity of γ-secretase, an intramembrane protease whose dysfunction has been implicated in the onset and progression of Alzheimer's disease.

Calculation of the thermal conductivity of human serum albumin (HSA) with equilibrium/non-equilibrium molecular dynamics approaches

BACKGROUND AND OBJECTIVE

Human serum albumin (HSA) controls the flow of numerous chemical structures and molecules in the cardiovascular system. So, thermal conductivity of this atomic compound is important in medicinal applications.

METHODS

In this work, the thermal conductivity of HSA is calculated with equilibrium/non-equilibrium molecular dynamic approaches. In these methods each HSA molecule is exactly represented by C, N, O and S atoms and their implemented dreiding potential. Finally by using Green-Kubo and Fourier's law the thermal conductivity of HSA/H₂O mixture is calculated.

RESULTS

Our calculated rates for thermal conductivity via equilibrium/non-equilibrium molecular dynamics methods are 0.496 W/m K and 0.448 W/m K, respectively. The calculated thermal conductivity for this structure was very close to the thermal conductivity calculated for water molecules which were reported by other research groups. Furthermore our simulated structures show that thermal conductivity of HAS/H₂O mixtures has inverse relation with HAS molecules numbers and temperature of simulated atomic structures.

CONCLUSIONS

Comparing thermal conductivity from equilibrium/non-equilibrium molecular dynamics methods for HAS/H₂O shows that EMD and NEMD results are reliable and EMD calculated results are higher than NEMD results.

Bovine serum albumin determination based on methylene blue detection by photothermal lens spectroscopy

We report on a new sensitive method, for bovine serum albumin quantification, which is based on the use of methylene blue as a labelling agent combined with photothermal lens detection. In the presence of sodium dodecyl sulfate, methylene blue forms a dimer which can react with bovine serum albumin producing dedimerization. We found that, the photothermal signal decreases proportional to the concentration of bovine serum albumin added to the system composed by dodecyl sulfate and methylene blue. Therefore, the change of the signal intensity is linearly proportional to the concentration of bovine serum albumin. Under the optimized analytical conditions, used in this work, the photothermal signal is linearly dependent on the concentration of bovine serum albumin in the range of 0.5 × 10^-6-7.5 × 10^-5 gmL^-1 with a regression coefficient R² = 0.9954. The relative standard deviation for BSA determination at 3.5 × 10^-5 gmL^-1 (n = 5) is 2.3% and the achieved detection limit is 3.5 × 10^-7 gmL^-1.

In Silico Docking of Alkylphosphocholine Analogs to Human Serum Albumin Predicts Partitioning and Pharmacokinetics

Alkylphosphocholine (APC) analogs are a novel class of broad-spectrum tumor-targeting agents that can be used for both diagnosis and treatment of cancer. The potential for clinical translation for APC analogs will strongly depend on their pharmacokinetic (PK) profiles. The aim of this work was to understand how the chemical structures of various APC analogs impact binding and PK. To achieve this aim, we performed in silico docking analysis, in vitro and in vivo partitioning experiments, and in vivo PK studies. Our results have identified 7 potential high-affinity binding sites of these compounds on human serum albumin (HSA) and suggest that the size of the functional group directly influences the albumin binding, partitioning, and PK. Namely, the bulkier the functional groups, the weaker the agent binds to albumin, the more the agent partitions onto lipoproteins, and the less time the agent spends in circulation. The results of these experiments provide novel molecular insights into the binding, partitioning, and PK of this class of compounds and similar molecules as well as suggest pharmacological strategies to alter their PK profiles. Importantly, our methodology may provide a way to design better drugs by better characterizing the PK profile for lead compound optimization.

Enterotoxigenic Escherichia coli Interferes FATP4-Dependent Long-Chain Fatty Acid Uptake of Intestinal Epithelial Enterocytes via Phosphorylation of ERK1/2-PPARγ Pathway

Sufficient fatty acid (FA) uptake from jejunal lumen is closely associated with pediatric growth. Enterotoxigenic Escherichia coli (ETEC), which poses a big threat to young mammals’ health, is also targeted on the jejunum, however, the effects on FA uptake is not understood yet. To explore the impacts of ETEC on the FA uptake ability of jejunum epithelial enterocytes during early life, we orally gavaged weaning piglets with ETEC K88 and found intestinal inflammation combined with compromised uptake of LCFA (C16:0, C18:0, C20:3, C20:4) except for C14:0 whose chain length is similar to medium chain fatty acid (MCFA). Furthermore, we observed reduced protein expression of TJs, fatty acid transport protein 4 (FATP4), peroxisome proliferator-activated receptor γ (PPARγ), phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2), and upregulated expression of p-PPARγ. In the in vitro study, we challenged polarized porcine intestine jejunum cell line IPEC-J2 with ETEC K88 and discovered similar results on intestinal barrier and expression of associated genes combined with morphological changes. Based on the constructed cellular model, we then determined lower uptake of BODIPY-labeled C16:0 without any difference in the uptake of BODIPY-labeled C12:0. The content of intracellular triglyceride which was mainly synthesized by LCFA concomitantly lowered down. Using gene knock down and overexpression, FATP4 was confirmed to be responsible for LCFA uptake. Moreover, ERK1/2 inhibitor U0126 and PPARγ antagonist T0070907 revealed ETEC could initiate cascaded phosphorylation of ERK1/2 and PPARγ resulting in hindered expression of FATP4. These results indicate ETEC challenge will cause dysfunction in FATP4-dependent LCFA uptake by phosphorylation of ERK1/2 and PPARγ. Furthermore, intestinal uptake of MCFA is in a FATP4-independent manner which is not easily disturbed by ETEC.

Oleic acid as a protein ligand improving intestinal absorption and ocular benefit of fucoxanthin in water through protein-based encapsulation

The oleic acid–protein delivery system can improve both the dispersibility and intestinal absorption of fucoxanthin in a hydrophilic environment.

A review of lipidation in the development of advanced protein and peptide therapeutics

The use of biologics (peptide and protein based drugs) has increased significantly over the past few decades. However, their development has been limited by their short half-life, immunogenicity and low membrane permeability, restricting most therapies to extracellular targets and administration by injection. Lipidation is a clinically-proven post-translational modification that has shown great promise to address these issues: improving half-life, reducing immunogenicity and enabling intracellular uptake and delivery across epithelia. Despite its great potential, lipidation remains an underutilized strategy in the clinical translation of lead biologics. We review how lipidation can overcome common challenges in biologics development as well as highlight gaps in our understanding of the effect of lipidation on therapeutic efficacy, where increased research and development efforts may lead to next-generation drugs.

Stearyl polyethylenimine complexed with plasmids as the core of human serum albumin nanoparticles noncovalently bound to CRISPR/Cas9 plasmids or siRNA for disrupting or silencing PD-L1 expression for immunotherapy

PURPOSE

In this study, a double emulsion method for complexing plasmids with stearyl poly-ethylenimine (stPEI) as the core to form human serum albumin (HSA) (plasmid/stPEI/HSA) nanoparticles (NPs) was developed for gene delivery by non-covalently binding onto plasmid/stPEI/HSA nanoparticles with CRISPR/Cas9 or siRNA, which disrupts or silences the expression of programmed cell death ligand-1 (PD-L1) for immunotherapy.

MATERIALS AND METHODS

Chemically synthesized stearyl-polyethyenimine (stPEI)/plasmids/HSA nanoparticles were maded by double emulsion method. They were characterized by dynamic light scattering (DLS), transmission electron microscope and also evaluated by in vitro study on CT 26 cells.

RESULTS

stPEI was synthesized by an N-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (EDC)-N-hydroxysuccinimide (NHS) reaction, and we found that the degree of substitution was ~1.0 when the ratio of PEI to stearic acid was 1:7 in the reaction. Then, two sgRNA sequences were selected and evaluated for their ability to knock out PD-L1 by decreasing its expression by about 20%. Based on the trend of particle size/zeta potential values as a function of ratio, F25P1 containing 25 μg of plasmid/stPEI/HSA NPs noncovalently bound to 1 μg plasmids via charge-charge interactions was found to be optimal. Its particle size was about 202.7±4.5 nm, and zeta potential was 12.60±0.15 mV. In an in vitro study, these NPs showed little cytotoxicity but high cellular uptake. Moreover, they revealed the potential for transfection and PD-L1 knockout in an in vitro cell model. Furthermore, F25P1S0.5 containing 25 μg of plasmid/stPEI/HSA NPs noncovalently bound to 1 μg of plasmids and 0.5 μg siRNA was prepared to simultaneously deliver plasmids and siRNA. An in vitro study demonstrated that the siRNA did not interfere with the transfection of plasmids and showed a high-transfection efficiency with a synergistic effect on inhibition of PD-L1 expression by 21.95%.

CONCLUSION

The plasmids/stPEI/HSA NPs could be a promising tool for gene delivery and improved immunotherapy.

Crosstalk between zinc and free fatty acids in plasma

In mammalian blood plasma, serum albumin acts as a transport protein for free fatty acids, other lipids and hydrophobic molecules including neurodegenerative peptides, and essential metal ions such as zinc to allow their systemic distribution. Importantly, binding of these chemically extremely diverse entities is not independent, but linked allosterically. One particularly intriguing allosteric link exists between free fatty acid and zinc binding. Albumin thus mediates crosstalk between energy status/metabolism and organismal zinc handling. In recognition of the fact that even small changes in extracellular zinc concentration and speciation modulate the function of many cell types, the albumin-mediated impact of free fatty acid concentration on zinc distribution may be significant for both normal physiological processes including energy metabolism, insulin activity, heparin neutralisation, blood coagulation, and zinc signalling, and a range of disease states, including metabolic syndrome, cardiovascular disease, myocardial ischemia, diabetes, and thrombosis.

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Serum albumin binds and transports both free fatty acids and Zn²⁺ ions

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Elevated plasma free fatty acids impair Zn²⁺ binding by albumin through an allosteric mechanism

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The resulting changes in plasma zinc speciation are thought to impact blood coagulation and may promote thrombosis

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Increased free Zn²⁺ may lead to enhanced zinc export from plasma and dysregulation of zinc homeostasis in multiple tissues

Nanoparticle size and production efficiency are affected by the presence of fatty acids during albumin nanoparticle fabrication

We have previously identified extensive glycation, bound fatty acids and increased quantities of protein aggregates in commercially available recombinant HSA (rHSA) expressed in Oryza sativa (Asian rice) (OsrHSA) when compared to rHSA from other expression systems. We propose these differences may alter some attributes of nanoparticles fabricated with OsrHSA, as studies have associated greater quantities of aggregates with increased nanoparticle diameters. To determine if this is the case, nanoparticles were fabricated with OsrHSA from various suppliers using ethanol desolvation and subsequent glutaraldehyde cross-linking. All nanoparticles fabricated with OsrHSA showed larger diameters of approximately 20 to 90nm than particles fabricated with either defatted bovine serum albumin (DF-BSA) (100.9 ± 2.8nm) or human plasma albumin (pHSA) (112.0 ± 4.0nm). It was hypothesized that the larger nanoparticle diameters were due to the presence of bound fatty acids and this was confirmed through defatting OsrHSA prior to particle fabrication which yielded particles with diameters similar to those fabricated with pHSA. For additional conformation, DF-BSA was incubated with dodecanoic acid prior to desolvation yielding particles with significantly larger diameters. Further studies showed the increased nanoparticle diameters were due to the bound fatty acids modulating electrostatic interactions between albumin nanoparticles during the desolvation and not changes in protein structure, stability or generation of additional albumin oligomers. Finally the presence of dodecanoic acid was shown to improve doxorubicin loading efficiency onto preformed albumin nanoparticles.

Cell culture models of fatty acid overload: Problems and solutions

High plasma levels of fatty acids occur in a variety of metabolic diseases. Cellular effects of fatty acid overload resulting in negative cellular responses (lipotoxicity) are often studied in vitro, in an attempt to understand mechanisms involved in these diseases. Fatty acids are poorly soluble, and thus usually studied when complexed to albumins such as bovine serum albumin (BSA). The conjugation of fatty acids to albumin requires care pertaining to preparation of the solutions, effective free fatty acid concentrations, use of different fatty acid species, types of BSA, appropriate controls and ensuring cellular fatty acid uptake. This review discusses lipotoxicity models, the potential problems encountered when using these cellular models, as well as practical solutions for difficulties encountered.

How Bound and Free Fatty Acids in Cellulose Films Impact Nonspecific Protein Adsorption

The effect of fatty acids and fatty acid esters to impair nonspecific protein adsorption on cellulose thin films is investigated. Thin films are prepared by blending trimethylsilyl cellulose solutions with either cellulose stearoyl ester or stearic acid at various ratios. After film formation by spin coating, the trimethylsilyl cellulose fraction of the films is converted to cellulose by exposure to HCl vapors. The morphologies and surface roughness of the blends were examined by atomic force microscopy revealing different feature shapes and sizes depending on the blend ratios. Nonspecific protein adsorption at the example of bovine serum albumin toward the blend thin films was tested by means of surface plasmon resonance spectroscopy in real-time. Incorporation of stearic acid into the cellulose leads to highly protein repellent surfaces regardless of the amount added. The stearic acid acts as a sacrificial compound that builds a complex with bovine serum albumin thereby inhibiting protein adsorption. For the blends where stearoyl ester is added to the cellulose films, the cellulose:cellulose stearoyl ester ratios of 3:1 and 1:1 lead to much lower nonspecific protein adsorption compared to pure cellulose, whereas for the other ratios, adsorption increases. Supplementary results were obtained from atomic force microscopy experiments performed in liquid during exposure to protein solution and surface free energy determinations.

Therapeutic Potential of Milk Whey

Milk whey—commonly known as cheese whey—is a by-product of cheese or casein in the dairy industry and contains usually high levels of lactose, low levels of nitrogenous compounds, protein, salts, lactic acid and small amounts of vitamins and minerals. Milk whey contains several unique components like immunoglobulins (Igs), lactoferrin (Lf), lactoperoxidase (Lp), glycomacropeptide (GMP) and sphingolipids that possess some important antimicrobial and antiviral properties. Some whey components possess anticancer properties such as sphingomyelin, which have the potential to inhibit colon cancer. Immunoglobulin-G (IgGs), Lp and Lf concentrated from whey participates in host immunity. IgGs binds with bacterial toxins and lowers the bacterial load in the large bowel. There are some whey-derived carbohydrate components that possess prebiotic activity. Lactose support lactic acid bacteria (such as Bifidobacteria and Lactobacilli). Stallic acids, an oligosaccharide in whey, are typically attached to proteins, and possess prebiotic properties. The uniqueness of whey proteins is due to their ability to boost the level of glutathione (GSH) in various tissues and also to optimize various processes of the immune system. The role of GSH is very critical as it protects the cells against free radical damage, infections, toxins, pollution and UV exposure. Overall GSH acts as a centerpiece of the body’s antioxidant defense system. It has been widely observed that individuals suffering from cancer, HIV, chronic fatigue syndrome and many other immune-compromising conditions have very poor levels of glutathione. The sulphur-containing amino-acids (cysteine and methionine) are also found in high levels in whey protein. Thus, the present review will focus on the therapeutic potential of milk whey such as antibiotic, anti-cancer, anti-toxin, immune-enhancer, prebiotic property etc.

Synthesis and study on the binding of thiazol-2(3H)-ylidine derivative with human serum albumin using spectroscopic and molecular docking methods

In this article, a facile and convenient synthesis of thiazol-2(3H)-ylidine derivatives of fatty acid (3a-c) is described. The binding of N'-(4,5-dimethyl-3-penylthiazol-2(3H)-ylidine)octadec-9-enehydrazide (3a) with human serum albumin (HSA) is explored using various spectral methods and molecular docking. Fluorescence quenching results show that 3a induces conformational changes in HSA and the polarity around the tryptophan residues is increased. Stern-Volmer quenching plots at different temperatures (298, 305 and 312 K) show that the fluorescence quenching mechanism is static quenching. Synchronous fluorescence, 3D fluorescence spectra, circular dichroism and Fourier transform infrared spectroscopy are used to determine the structural change in HSA on interaction with 3a. Förster resonance energy transfer analysis shows that the binding distance (r₀  = 2.78 nm) between HSA (Trp214) and 3a is within the of range 2-8 nm for quenching to occur. The molecular docking study also confirms that 3a is located in subdomain IIA (site I) of HSA and is stabilized by hydrogen bonding and hydrophobic forces.

ITC and NMR Analysis of the Encapsulation of Fatty Acids within a Water-Soluble Cavitand and its Dimeric Capsule

We report here NMR and ITC studies of the binding of ionizable guests (carboxylate acids) to a deep-cavity cavitand. These studies reveal that the shortest guests favored 1:1 complex formation, but the longer the alkyl chain the more the 2:1 host-guest capsule is favored. For intermediate-sized guests, the equilibrium between these two states is controlled by pH; at low values the capsule containing the carboxylic acid guest is favored, whereas as the pH is raised deprotonation of the guest favors the 1:1 complex. Interestingly, for one host-guest pair the energy required to de-cap the 2:1 capsular complex and form the 1:1 complex is sufficient to shift the pK_a of the guest by ~ 3-4 orders of magnitude (4.1-5.4 kcal mol^-1). The two largest guests examined form stable 2:1 capsules, with in both cases the guest adopting a relatively high energy J-shaped motif. Furthermore, these 2:1 complexes are sufficiently stable that at high pH guest deprotonation occurs without de-capping of the capsule.

Biocompatibility of polysebacic anhydride microparticles with chondrocytes in engineered cartilage

One of main challenges in developing clinically relevant engineered cartilage is overcoming limited nutrient diffusion due to progressive elaboration of extracellular matrix at the periphery of the construct. Macro-channels have been used to decrease the nutrient path-length; however, the channels become occluded with matrix within weeks in culture, reducing nutrient diffusion. Alternatively, microparticles can be imbedded throughout the scaffold to provide localized nutrient delivery. In this study, we evaluated biocompatibility of polysebacic anhydride (PSA) polymers and the effectiveness of PSA-based microparticles for short-term delivery of nutrients in engineered cartilage. PSA-based microparticles were biocompatible with juvenile bovine chondrocytes for concentrations up to 2mg/mL; however, cytotoxicity was observed at 20mg/mL. Cytotoxicity at high concentrations is likely due to intracellular accumulation of PSA degradation products and resulting lipotoxicity. Cytotoxicity of PSA was partially reversed in the presence of bovine serum albumin. In conclusion, the findings from this study demonstrate concentration-dependent biocompatibility of PSA-based microparticles and potential application as a nutrient delivery vehicle that can be imbedded in scaffolds for tissue engineering.

Binding of Fatty Acid Amide Amphiphiles to Bovine Serum Albumin: Role of Amide Hydrogen Bonding

The study of protein-surfactant interactions is important because of the widespread use of surfactants in industry, medicine, and pharmaceutical fields. Sodium N-lauroylsarcosinate (SL-Sar) is a widely used surfactant in cosmetics, shampoos. In this paper, we studied the interactions of bovine serum albumin (BSA) with SL-Sar and sodium N-lauroylglycinate (SL-Gly) by use of a number of techniques, including fluorescence and circular dichroism spectroscopy and isothermal titration calorimetry. The binding strength of SL-Sar is stronger than that of structurally similar SL-Gly, which differs only by the absence of a methyl group in the amide nitrogen atom. Also, these two surfactants exhibit different binding patterns with the BSA protein. The role of the amide bond and hence the surfactant headgroup in the binding mechanism is discussed in this paper. It was observed that while SL-Sar destabilized, SL-Gly stabilized the protein structure, even at concentrations less than the critical micelle concentration (cmc) value. The thermodynamics of surfactant binding to BSA was studied by use of ITC. From the ITC results, it is concluded that three molecules of SL-Sar in contrast to only one molecule of SL-Gly bind to BSA in one set of binding sites at room temperature. However, on increasing temperature four molecules of SL-Gly bind to the BSA through H-bonding and van der Waals interactions, due to loosening of the BSA structure. In contrast, with SL-Sar the binding process is enthalpy driven, and very little structural change of BSA was observed at higher temperature.

Bovine β-lactoglobulin/fatty acid complexes: binding, structural, and biological properties

Ligand-binding properties of β-lactoglobulin (β-lg) are well documented, but the subsequent biological functions are still unclear. Focusing on fatty acids/β-lg complexes, the structure-function relationships are reviewed in the light of the structural state of the protein (native versus non-native aggregated proteins). After a brief description of β-lg native structure, the review takes an interest in the binding properties of native β-lg (localization of binding sites, stoichiometry, and affinity) and the way the interaction affects the biological properties of the protein and the ligand. The binding properties of non-native aggregated forms of β-lg that are classically generated during industrial processing are also related. Structural changes modify the stoichiometry and the affinity of β-lg for fatty acids and consequently the biological functions of the complex. Finally, the fatty acid-binding properties of other whey proteins (α-lactalbumin, bovine serum albumin) and some biological properties of the complexes are also addressed. These proteins affect β-lg/fatty acids complex in whey given their competition with β-lg for fatty acids.

Modulated photophysics of a cationic DNA-staining dye inside protein bovine serum albumin: study of binding interaction and structural changes of protein

The binding affinity of cationic DNA-staining dye, propidium iodide, with transport protein, bovine serum albumin, has been explored using UV-vis absorption, fluorescence, and circular dichroism spectroscopy. Steady state and time resolved fluorescence studies authenticate that fluorescence quenching of bovine serum albumin by propidium iodide is due to bovine serum albumin-propidium iodide complex formation. Thermodynamic parameters obtained from temperature dependent spectral studies cast light on binding interaction between the probe and protein. Site marker competitive binding has been encountered using phenylbutazone and flufenamic acid for site I and site II, respectively. Energy transfer efficiency and distance between bovine serum albumin and propidium iodide have been determined using Förster mechanism. Structural stabilization or destabilization of protein by propidium iodide has been investigated by urea denaturation study. The circular dichroism study as well as FT-IR measurement demonstrates some configurational changes of the protein in presence of the dye. Docking studies support the experimental data thereby reinforcing the binding site of the probe to the subdomain IIA of bovine serum albumin.

Fatty acids as therapeutic auxiliaries for oral and parenteral formulations

Many drugs have decreased therapeutic activity due to issues with absorption, distribution, metabolism and excretion. The co-formulation or covalent attachment of drugs with fatty acids has demonstrated some capacity to overcome these issues by improving intestinal permeability, slowing clearance and binding serum proteins for selective tissue uptake and metabolism. For orally administered drugs, albeit at low level of availability, the presence of fatty acids and triglycerides in the intestinal lumen may promote intestinal uptake of small hydrophilic molecules. Small lipophilic drugs or acylated hydrophilic drugs also show increased lymphatic uptake and enhanced passive diffusional uptake. Fatty acid conjugation of small and large proteins or peptides has exhibited protracted plasma half-lives, site-specific delivery and sustained release upon parenteral administration. These improvements are most likely due to associations with lipid-binding serum proteins, namely albumin, LDL and HDL. These molecular interactions, although not fully characterized, could provide the ability of using the endogenous carrier systems for improving therapeutic outcomes.

NMR reveals molecular interactions and dynamics of fatty acid binding to albumin

BACKGROUND

The molecular details of fatty acid (FA) interactions with albumin are fundamental to understanding transport in the plasma and cellular utilization of these key nutrients and building blocks of membranes.

SCOPE OF REVIEW

This review focuses on the development and application of NMR methods to study FA binding to albumin [bovine (BSA) and human (HSA)]. The key strategy was to use (13)C enrichment of a specific carbon in the FA as a non-perturbing probe to permit visualization of the small ligand complexed to the very large protein. NMR contributions to illuminating molecular interactions and FA dynamics are summarized from three decades of studies.

MAJOR CONCLUSIONS

Our early studies detected multiple binding sites that we hypothesized were distinguished because of the unique tertiary structure of the protein in close proximity to the FA labeled carbon in each site. Later crystallographic structures revealed the presence of polar and charged amino acid side chains near the carboxyl carbon of the FA and unique tertiary structures lining all of the FA binding pockets. In collaboration with the crystallography group, several FA sites in the crystalline state were matched with NMR resonances in the solution state. With the newest application of NMR, 2D NMR spectroscopy detected nine binding sites, and three were located in the crystal structure through displacement of drugs with identified sites.

GENERAL SIGNIFICANCE

NMR spectroscopy utilizing the FA as a probe allows characterization of site-specific interactions, molecular motions within binding sites, the order of filling and removal of FA from sites. This article is part of a Special Issue entitled Serum Albumin.

Allosteric modulation of zinc speciation by fatty acids

BACKGROUND

Serum albumin is the major protein component of blood plasma and is responsible for the circulatory transport of a range of small molecules that include fatty acids, hormones, metal ions and drugs. Studies examining the ligand-binding properties of albumin make up a large proportion of the literature. However, many of these studies do not address the fact that albumin carries multiple ligands (including metal ions) simultaneously in vivo. Thus the binding of a particular ligand may influence both the affinity and dynamics of albumin interactions with another.

SCOPE OF REVIEW

Here we review the Zn(2+) and fatty acid transport properties of albumin and highlight an important interplay that exists between them. Also the impact of this dynamic interaction upon the distribution of plasma Zn(2+), its effect upon cellular Zn(2+) uptake and its importance in the diagnosis of myocardial ischemia are considered.

MAJOR CONCLUSIONS

We previously identified the major binding site for Zn(2+) on albumin. Furthermore, we revealed that Zn(2+)-binding at this site and fatty acid-binding at the FA2 site are interdependent. This suggests that the binding of fatty acids to albumin may serve as an allosteric switch to modulate Zn(2+)-binding to albumin in blood plasma.

GENERAL SIGNIFICANCE

Fatty acid levels in the blood are dynamic and chronic elevation of plasma fatty acid levels is associated with some metabolic disorders such as cardiovascular disease and diabetes. Since the binding of Zn(2+) to albumin is important for the control of circulatory/cellular Zn(2+) dynamics, this relationship is likely to have important physiological and pathological implications. This article is part of a Special Issue entitled Serum Albumin.

Correspondence of fatty acid and drug binding sites on human serum albumin: a two-dimensional nuclear magnetic resonance study

The ability of human serum albumin (HSA) to bind fatty acids (FA) in multiple sites has been revealed by many studies. Here we detect and characterize nine individual binding sites by two-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopy of 18-[(13)C]-oleic acid (OA) complexed with HSA. We characterize site-specific FA binding by addition of (i) different FA molar ratios (from 1:1 to 4:1 OA:HSA) to observe the order of filling and occupancy of binding sites; (ii) methyl-β-cyclodextrin, as a FA acceptor, to observe the dissociation of FA; and (iii) drugs (with known binding sites in the crystal structure) to reveal the correspondence of three NMR peaks with sites in the crystal structure. At 1:1 and 2:1 OA:HSA ratios, three sites were shown to fill sequentially. These high-affinity sites were well resolved from additional sites (one medium-affinity and five low-affinity) observed at 3:1 and 4:1 OA:HSA ratios. Methyl-β-cyclodextrin extracted OA from individual sites in the reverse order of filling. FA bound in three low-affinity sites were displaced by drugs shown to bind in crystalline HSA to FA sites 7 and 3 (Sudlow's drug sites I and II, respectively) and FA site 6. With this strategy, 2D NMR spectral analysis permits site-specific characterization of the binding of drugs and FA and provides a sensitive probe of the mutual effects of FA and ligand binding.