Acids Of Different Chain Lengths Research Articles

Molecular dynamics simulations of lipid composition and its impact on structural and dynamic properties of skin membrane

The stratum corneum (SC) plays the most important role in the absorption of topical and transdermal drugs. In this study, we developed a multi-layered SC model using coarse-grained molecular dynamics (CGMD) simulations of ceramides, cholesterol, and fatty acids in equimolar proportions, starting from two different initial configurations. In the first approach, all ceramide molecules were initially in the hairpin conformation, and the membrane bilayers were pre-formed. In the second approach, ceramide molecules were introduced in either the hairpin or splayed conformation, with the lipid molecules randomly oriented at the start of the simulation. The aim was to evaluate the effects of lipid chain length on the structural and dynamic properties of SC. By incorporating ceramides and fatty acids of different chain lengths, we simulated the SC membrane in healthy and diseased states. We calculated key structural properties including the thickness, normalized lipid area, lipid tail order parameters, and spatial ordering of the lipids from each system. The results showed that systems with higher ordering and structural integrity contained an equimolar ratio of ceramides (chain length of 24 carbon atoms), fatty acids with chain lengths ≥ of 20 carbon atoms, and cholesterol. In these systems, strong apolar interactions between the ceramide and fatty acid long acyl chains restricted the mobility of the lipid molecules, thereby maintaining a compact lipid headgroup region and high order in the lipid tail region. The simulations also revealed distinct flip-flop mechanisms for cholesterol and fatty acid within the multi-layered membrane. Cholesterol is mostly diffused through the tail-tail interface region of the membrane and could flip-flop in the same bilayer. In contrast, fatty acids flip-flopped between adjacent leaflets of two bilayers in which the tails crossed the thinner headgroup region of the membrane. To conclude, our SC model provides mechanistic insights into lipid mobility and is flexible in its design and composition of different lipids, enabling studies of varying skin conditions.

Modulating Phase Behavior in Fatty Acid-Modified Elastin-like Polypeptides (FAMEs): Insights into the Impact of Lipid Length on Thermodynamics and Kinetics of Phase Separation.

Although post-translational lipidation is prevalent in eukaryotes, its impact on the liquid-liquid phase separation of disordered proteins is still poorly understood. Here, we examined the thermodynamic phase boundaries and kinetics of aqueous two-phase system (ATPS) formation for a library of elastin-like polypeptides modified with saturated fatty acids of different chain lengths. By systematically altering the physicochemical properties of the attached lipids, we were able to correlate the molecular properties of lipids to changes in the thermodynamic phase boundaries and the kinetic stability of droplets formed by these proteins. We discovered that increasing the chain length lowers the phase separation temperature in a sigmoidal manner due to alterations in the unfavorable interactions between protein and water and changes in the entropy of phase separation. Our kinetic studies unveiled remarkable sensitivity to lipid length, which we propose is due to the temperature-dependent interactions between lipids and the protein. Strikingly, we found that the addition of just a single methylene group is sufficient to allow tuning of these interactions as a function of temperature, with proteins modified with C7-C9 lipids exhibiting non-Arrhenius dependence in their phase separation, a behavior that is absent for both shorter and longer fatty acids. This work advances our theoretical understanding of protein-lipid interactions and opens avenues for the rational design of lipidated proteins in biomedical paradigms, where precise control over the phase separation is pivotal.

Wood Esterification by Fatty Acids Using Trifluoroacetic Anhydride as an Impelling Agent and Its Application for the Synthesis of a New Bioplastic.

Fatty acids (FA) and their derivatives with long alkyl chain structures are good candidates for wood esterification to confer thermoplastic properties to wood. Nevertheless, they do not react easily with hydroxyl groups of wood. In this study, we investigated the reactivity of wood with various fatty acids of different chain lengths using trifluoroacetic anhydride (TFAA) as the impelling agent in various reaction conditions. Generally, the esterification of fatty acids without solvents resulted in higher Weight Percentage Gain (WPG) and ester content than the reaction in the presence of CH2Cl2. The esterification reaction could be performed effectively at room temperature, though an increased reaction temperature provoked degradation of the esterified wood. WPG of 67% was obtained for the C3 and 253% for the C16 alkyl chain analogs, respectively. Nevertheless, the ester content was fairly uniform, with values between 10.60 and 11.81 mmol ester/gram of wood for all chain lengths. A higher quantity of reagent led to higher ester content, which tended to stabilize after a ratio of 1:4 wood and TFAA/FA. The esterification reaction was performed rapidly, with an ester content between 7.65 and 9.94 mmol ester/gram of wood being achieved only after 15 min of reaction. Fourier transform infrared spectroscopy (FTIR) analysis was performed to confirm the drastic chemical changes of wood before and after esterification. Morphological observation by scanning electron microscope (SEM), softening measurement by thermomechanical analysis (TMA), and contact angle measurements demonstrated the possibility of esterified spruce wood being applied as a new bioplastic.

Thermoplastic translucent film from wood and fatty acids by solvent free esterification: Influence of fatty acid chain length

Transforming wood into thermoplastic material has long been a challenging research topic, nevertheless the application of this technology to the industrial level hampered because of the complex method available. Here, we demonstrate a promising method converting spruce sawdust into thermoplastic material by esterification with various fatty acids of different chain length (4–18 carbon). The esterification was carried out using trifluoroacetic anhydride (TFAA) as a promoter. Weight percentage gain (WPG) of 70% was obtained for the shortest fatty acid used in this study (C4) and increased with the length of fatty acid chain to 271.3% (C18) and ester content were uniformly achieved ranged between 9.10 and 11.27 mmol/gram of wood. Chemical analysis by FTIR and CP/MAS 13C NMR revealed hydroxyl group of esterified wood was replaced by the ester group and alkyl chain. XRD analysis showed decrystallization of cellulose in esterified spruce sawdust. Esterified wood exhibit higher thermal stability observed by TGA and DSC, and presented several softening temperatures observed by TMA. Thermoplastic, translucent, and flexible film were obtained after hot pressing. In contrast with previous research, our study revealed that thermoplastic wood sheet could be obtained by esterification without solvent and at room temperature after only 4 h of reaction.

Preparation of Self-Assembled Nanoparticle–Polymer Hybrids from Modified Silica Nanoparticles and Polystyrene-Block-Polyacrylic Acid Vesicles via the Co-Precipitation Method

Nanoparticle-polymer hybrids are becoming increasingly important because seemingly contrasting properties, such as mechanical stability and high elasticity, can be combined into one material. In particular, hybrids made of self-assembled polymers are of growing interest since they exhibit high structural precision and diversity and the subsequent reorganization of the nanoparticles is possible. In this work, we show, for the first time, how hybrids of silica nanoparticles and self-assembled vesicles of polystyrene-block-polyacrylic acid can be prepared using the simple and inexpensive method of co-precipitation, highlighting in particular the challenges of using silica instead of other previously well-researched materials, such as gold. The aim was to investigate the influence of the type of modification and the particle size of the silica nanoparticles on the encapsulation and structure of the polymer vesicles. For this purpose, we first needed to adjust the surface properties of the nanoparticles, which we achieved with a two-step modification procedure using APTES and carboxylic acids of different chain lengths. We found that silica nanoparticles modified only with APTES could be successfully encapsulated, while those modified with APTES and decanoic acid resulted in vesicle agglomeration and poor encapsulation due to their strong hydrophobicity. In contrast, no negative effects were observed when different particle sizes (20 nm and 45 nm) were examined.

Derivatizing of Fast Pyrolysis Bio-Oil and Coprocessing in Fixed Bed Hydrotreater

In several countries forest-based biofuels are being developed and to some extent also deployed. Fast pyrolysis bio-oil produced from, for example, sawdust, has now been coprocessed in fluid catalytic cracking refinery units in a number of commercial trials. However, this application is limited to about 10% of the total feed, and coprocessing in conventional fixed bed hydrotreaters is necessary to reach the high potential with this feedstock. Feeding and upgrading of fast pyrolysis bio-oil in a fixed bed reactor configuration is still problematic due to the inherent bio-oil properties. Stabilization of reactive compounds in fast pyrolysis bio-oil and mild hydrotreatment in a separate refining unit prior to refinery integration has therefore been developed the past decade. Another approach, presented here, involves complete dewatering of fast pyrolysis bio-oil by azeotropic distillation using mesityl oxide as the solvent, followed by conversion of the abundant hydroxyl compounds via mixed anhydride esterification methodology using an external source of mixed carboxylic acids of different chain lengths originating from renewable tall oil fatty acids, providing a lipophilic feed component. Dewatering and derivatizing were carried out in reactors up to 50 dm3 with a mass ratio of fast pyrolysis bio-oil to tall oil fatty acid of 10:13. The produced lipophilic oils were miscible with a petroleum light gas oil fraction and exhibited superior stability even after accelerated aging at elevated temperature (80 °C). The derivatized oils were thus mixed with light gas oil, with a proportion of 30 wt % derivatized oil in final blends and hydrotreated continuously in pilot fixed bed reactors for 14 days at 4 operating conditions without plugging or excessive exotherms. The test conditions were varied; the reactor pressure was either 55 or 80 bar, temperature 380 or 400 °C, and liquid hourly space velocity either 1 or 2 h–1 during the hydrotreatment. Successful hydrodeoxygenation and desulfurization were accomplished, whereas an increasing nitrogen concentration could be observed in the liquid products with the particular catalyst and reaction conditions employed. The observed hydrogen consumption (15–20 g/kg feed) was compared with the stoichiometric consumption for direct deoxygenation and with typical consumptions for industrial hydrotreated vegetable oil processing. The measured biogenic carbon content in hydrotreated liquid products (26.7%) agreed extremely well with the calculated biogenic carbon content in the hydrotreating feed (26.6%) that consisted of the blend of derivatized oil and petroleum light gas oil. The overall results are very promising since simple unit operations can be used to produce derivatized fast pyrolysis bio-oils that do not need additional standalone hydrotreating units but can be coprocessed in existing ones.

Nanozyme-Based Lateral Flow Immunoassay (LFIA) for Extracellular Vesicle Detection.

Extracellular vesicles (EVs) are biological nanoparticles of great interest as novel sources of biomarkers and as drug delivery systems for personalized therapies. The research in the field and clinical applications require rapid quantification. In this study, we have developed a novel lateral flow immunoassay (LFIA) system based on Fe3O4 nanozymes for extracellular vesicle (EV) detection. Iron oxide superparamagnetic nanoparticles (Fe3O4 MNPs) have been reported as peroxidase-like mimetic systems and competent colorimetric labels. The peroxidase-like capabilities of MNPs coated with fatty acids of different chain lengths (oleic acid, myristic acid, and lauric acid) were evaluated in solution with H2O2 and 3,3,5,5-tetramethylbenzidine (TMB) as well as on strips by biotin–neutravidin affinity assay. As a result, MNPs coated with oleic acid were applied as colorimetric labels and applied to detect plasma-derived EVs in LFIAs via their nanozyme effects. The visual signals of test lines were significantly enhanced, and the limit of detection (LOD) was reduced from 5.73 × 107 EVs/μL to 2.49 × 107 EVs/μL. Our work demonstrated the potential of these MNPs as reporter labels and as nanozyme probes for the development of a simple tool to detect EVs, which have proven to be useful biomarkers in a wide variety of diseases.

Response of Trypanosoma brucei to Exogenous Fatty Acids in Low Lipid Conditions

Trypanosoma brucei is an extracellular parasite that causes African Sleeping Sickness and is endemic to the sub‐Saharan African region. The parasite's extracellular nature forces the parasite to adapt to its host's environment. One of the regulatory mechanisms is to regulate fatty acid synthesis enzymes in response to exogenous fatty acids. Our previous study showed that the insect‐host procyclic form (PF) T. brucei regulates the activity and expression level of acetyl‐CoA carboxylase (ACC) when grown in media containing different lipid levels. PF in low lipid media has an elevated ACC activity but lower ACC protein level than in high lipid media. We also observed that the addition of C18:0 to PF in low lipid media reduced ACC activity and increased growth rate, which showed an environmental response to the exogenous fatty acid level. Here, we observe the growth and the ACC level of low lipid‐adapted PF T. brucei after treatment with fatty acids of different chain lengths. We did not observe a significant change in the ACC protein level; however, we observed significant growth differences with the addition of different fatty acids, and some of these effects were cell density‐dependent. These data suggested that adding fatty acids changes ACC's activity and pattern of PF growth in low lipid but does not change PF's ACC expression level. Future studies will investigate whether different fatty acids regulate ACC activity by phosphorylation, allosteric regulation, or a combination of both mechanisms.

Development of oxaalkyne and alkyne fatty acids as novel tracers to study fatty acid beta-oxidation pathways and intermediates

Fatty acid beta-oxidation is a key process in mammalian lipid catabolism. Disturbance of this process results in severe clinical symptoms, including dysfunction of the liver, a major beta-oxidizing tissue. For a thorough understanding of this process, a comprehensive analysis of involved fatty acid and acyl-carnitine intermediates is desired, but capable methods are lacking. Here, we introduce oxaalkyne and alkyne fatty acids as novel tracers to study the beta-oxidation of long- and medium-chain fatty acids in liver lysates and primary hepatocytes. Combining these new tracer tools with highly sensitive chromatography and mass spectrometry analyses, this study confirms differences in metabolic handling of fatty acids of different chain length. Unlike longer chains, we found that medium-chain fatty acids that were activated inside or outside of mitochondria by different acyl-CoA synthetases could enter mitochondria in the form of free fatty acids or as carnitine esters. Upon mitochondrial beta-oxidation, shortened acyl-carnitine metabolites were then produced and released from mitochondria. In addition, we show that hepatocytes ultimately also secreted these shortened acyl chains into their surroundings. Furthermore, when mitochondrial beta-oxidation was hindered, we show that peroxisomal beta-oxidation likely acts as a salvage pathway, thereby maintaining the levels of shortened fatty acid secretion. Taken together, we conclude that this new method based on oxaalkyne and alkyne fatty acids allows for metabolic tracing of the beta-oxidation pathway in tissue lysate and in living cells with unique coverage of metabolic intermediates and at unprecedented detail.

Fatty acylation enhances the cellular internalization and cytosolic distribution of a cystine-knot peptide

SummaryDelivering peptides into cells could open up possibilities for targeting intracellular proteins. Although fatty acylation of peptide therapeutics improves their systemic half-life, it remains unclear how it influences their cellular uptake. Here, we demonstrate that a fatty acylated peptide exhibits enhanced cellular internalization and cytosolic distribution compared to the un-acylated version. By using a cystine-knot peptide as a model system, we report an efficient strategy for site-specific conjugation of fatty acids. Peptides modified with fatty acids of different chain lengths entered cells through clathrin-mediated and macropinocytosis pathways. The cellular uptake was mediated by the length of the hydrocarbon chain, with myristic acid conjugates displaying the highest distribution across the cytoplasm including the cytosol, and endomembranes of the ER, Golgi and mitochondria. Our studies demonstrate how fatty acylation improves the cellular uptake of peptides, and lay the groundwork for future development of bioactive peptides with enhanced intracellular distribution.

Detecting the selection signatures in Chinese Duroc,Landrace, Yorkshire, Liangshan, and Qingyu pigs.

Here we used two kinds of chips data from 5 pig breeds, Chinese Duroc (DD), Landrace (LL), Yorkshire (YY), Liangshan (LS), and Qingyu pigs (QY) in China to identify genes which show evidence of selection during domestication. Four breed pairs, LS-YY, QY-YY, DD-YY, and LL-YY pair, were performed to detect selection signatures using the Fst method. Then we identified a list of genes that played key roles in domestication and artificial selection. For example, the PTPRM gene was shared in LS-YY, QY-YY, and DD-YY pairs and it regulates a variety of cellular processes including cell growth, differentiation as signaling molecules. The HACD3 gene was shared in QY-YY and DD-YY pairs, and the HACD3 protein is involved in the production of very long-chain fatty acids of different chain lengths. Besides, the MYH11 gene that related to muscle contraction was found in LS-YY and LL-YY pair. These results suggested that genes related to immunity, disease resistance, and metabolism were subjected to strong selection pressure in Chinese domestic pigs in the progress of domestication and evolution; however, genes related to appearance, production performance, and reproduction were undergone strong artificial selection in commercial pig breeds.

Cardiometabolic impacts of saturated fatty acids: are they all comparable?

In last decades, a phenomenon named nutrition transition has been observed in many countries around the world. It has been characterised by increased consumption of fat-rich diets, predisposing to cardiometabolic diseases and high prevalence of the obesity. In the dietary recommendations cited to prevent metabolic diseases, there is a consensus to decrease intake of saturated fatty acids (SFA) to less than 10% of total energy intake, as recommended by the Food Safety Authorities. However, fatty acids of different chain lengths may exhibit different cardiometabolic effects. Thus, our major aim was to review the cardiometabolic effects of different classes of SFA according to carbon chain length, i.e. short-, medium- and long-chains. The review emphasises that not all SFA may have harmful cardiometabolic effects since short- and medium-chain SFA can provide beneficial health effects and participate to the prevention of metabolic disorders.

The response of Trypanosoma brucei to Exogenous Fatty Acids in Low Lipid Conditions

Trypanosoma brucei is an extracellular parasite that causes African Sleeping Sickness and is endemic to the sub-Saharan African region. The parasite's extracellular nature forces the parasite to adapt to its host's environment. One of the regulatory mechanisms is to regulate fatty acid synthesis enzymes in response to exogenous fatty acids. Our previous study showed that the insect-host procyclic form (PF) T. brucei regulates the activity and expression level of acetyl-CoA carboxylase (ACC) when grown in media containing different lipid levels. PF in low lipid media has an elevated ACC activity but lower ACC protein level than in high lipid media. We also observed that the addition of C18:0 to PF in low lipid media reduced ACC activity and increased growth rate, which showed an environmental response to the exogenous fatty acid level. Here, we observe the growth and the ACC level of low lipid-adapted PF T. brucei after treatment with fatty acids of different chain lengths. We did not observe a significant change in the ACC protein level. However, we observed significant growth differences with the addition of different fatty acids, and some of these effects were cell density-dependent. These data suggested that the addition of fatty acids changes ACC's activity and PF growth pattern in low lipid, but does not change PF's ACC expression level. Future studies will investigate whether different fatty acids regulate ACC activity by phosphorylation, allosteric regulation, or a combination of both mechanisms.

Sweet surfactants I: Fatty acid esters of sucralose

Surface active agents derived from the non-toxic sweetener sucralose and fatty acids of different chain length were synthesized. Obtained compounds were characterized chemically and with regard to their properties as emulsifying agents, antimicrobial preservatives and fat-soluble sweeteners. Results show that sucralose-fatty acid esters are possible multi-purpose additives, compatible with both cosmetic and edible emulsions, as well as purely oil-based, waterless formulations. Their relative effectiveness in those applications varies, and is highly dependent on the fatty acid chain length, with hydrophobic/hydrophilic character strongly impacting both emulsifying and antimicrobial properties. While the structural differences between sucrose and sucralose proved to be enough to push all of the newly synthesized compounds out of the detergent/solubilizer category of surfactants, the retention of the substrate’s high sweetness is an indication that non-bitter compounds with washing capabilities are possible to obtain.

Magnetically separable heteropolyanion based ionic liquid as a heterogeneous catalyst for ultrasound mediated biodiesel production through esterification of fatty acids

The catalytic production of biodiesel has attracted the attention of academic and commercial research due to its higher efficiency and environmental sustainability. In this article, a magnetically separable heteropolyanion-based ionic liquid was synthesized, and its catalytic activity was evaluated for biodiesel production through the esterification of long-chain fatty acid under ultrasonic irradiation. The influence of different experimental parameters like amount of catalyst, the molar ratio of alcohol to acid, reaction temperature and time were evaluated. The article also describes the effect of the varying alcohols and fatty acids of different chain lengths, shapes, and unsaturation on esterification reaction. Moreover, after the reaction's completion catalyst can be easily separated from the reaction mixture through the external magnet and could be reused up to six reaction cycles without losing its catalytic efficiency.

Effect of chain length and saturation of the fatty acids in dietary triglycerides on lipid metabolism in Wistar rats.

We investigated the effect of the chain length and the degree of saturation of fatty acids in dietary triglycerides on serum lipid profiles and hepatic lipid metabolism in Wistar rats. Fat component of the basal diet (soybean oil) was replaced with fats with fatty acids of different chain lengths and saturation and the serum lipids were monitored for 150days. Principal component (PC) analysis of serum lipid components was related to chain length and saturation. The combined effect of chain length and saturation on PC 1 scores was evaluated by multiple regression analysis. The results indicated that average chain length of the fatty acids of triglycerides has a higher influence on the quality of serum lipid parameters than the average degree of saturation. Expression of selected genes responsible for lipid metabolism showed similar trends in medium chain saturated and long chain polyunsaturated diet groups. PRACTICAL APPLICATIONS: Dietary lipids contain a wide range of saturated and unsaturated fatty acids with different chain lengths. Overall contribution of these different fatty acids decides the health effects of the lipids in the diet. Present study shows that the fats with medium chains and higher degree of saturation and fats with long chains and higher degree of unsaturation (lower degree of saturation) affect serum lipid parameters and expression of hepatic genes involved in the lipid metabolism in a similar manner. Such information is important for physicians to plan dietary schemes to improve the nutritional health and manage the noncommunicable diseases.

Epoxidized soybean oil modified using fatty acids as tougheners for thermosetting epoxy resins: Part 1

AbstractA series of bio‐rubber (BR) reactive tougheners for thermosetting epoxy resins was prepared by grafting renewable saturated fatty acids of different chain lengths (C6‐C14) onto epoxidized soybean oil (ESO) at varying molar ratios. The tunable nature of the BR systems derives from the architecture and functionality of naturally occurring molecules. Control of BR reactivity and molecular weight by varying the degree of grafting and the chain length of the fatty acid was demonstrated. The BR‐toughened samples were prepared by blending BRs with diglycidyl ether of bisphenol A (DGEBA), Epon 828, and stoichiometrically curing the mixture using an aromatic amine hardener, diethyl toluene diamine (Epikure W). Fracture surface morphology studies showed that tuning of phase separated particle sizes was possible depending on the BR type and weight fraction. The resulting toughening effect was evaluated by measuring the fracture toughness of control and toughened polymer samples. The use of BRs significantly improved the critical strain energy release rate and critical stress intensity factor values of thermosetting polymer samples without significantly reducing Tg and modulus. In addition to toughening and adding renewable content to petroleum‐based thermosetting epoxy systems these new tougheners have low viscosity compared to common alternatives and aid ease of processing.

Pharmacology of Free Fatty Acid Receptors and Their Allosteric Modulators.

The physiological function of free fatty acids (FFAs) has long been regarded as indirect in terms of their activities as educts and products in metabolic pathways. The observation that FFAs can also act as signaling molecules at FFA receptors (FFARs), a family of G protein-coupled receptors (GPCRs), has changed the understanding of the interplay of metabolites and host responses. Free fatty acids of different chain lengths and saturation statuses activate FFARs as endogenous agonists via binding at the orthosteric receptor site. After FFAR deorphanization, researchers from the pharmaceutical industry as well as academia have identified several ligands targeting allosteric sites of FFARs with the aim of developing drugs to treat various diseases such as metabolic, (auto)inflammatory, infectious, endocrinological, cardiovascular, and renal disorders. GPCRs are the largest group of transmembrane proteins and constitute the most successful drug targets in medical history. To leverage the rich biology of this target class, the drug industry seeks alternative approaches to address GPCR signaling. Allosteric GPCR ligands are recognized as attractive modalities because of their auspicious pharmacological profiles compared to orthosteric ligands. While the majority of marketed GPCR drugs interact exclusively with the orthosteric binding site, allosteric mechanisms in GPCR biology stay medically underexploited, with only several allosteric ligands currently approved. This review summarizes the current knowledge on the biology of FFAR1 (GPR40), FFAR2 (GPR43), FFAR3 (GPR41), FFAR4 (GPR120), and GPR84, including structural aspects of FFAR1, and discusses the molecular pharmacology of FFAR allosteric ligands as well as the opportunities and challenges in research from the perspective of drug discovery.

Antiglycative and anti-inflammatory effects of lipophilized tyrosol derivatives

To expand the application of tyrosol, a series of lipophilized tyrosol derivatives were synthesized via esterification of tyrosol with fatty acids of different chain lengths. The antiglycative activity of tyrosol esters so prepared was subsequently examined in the bovine serum albumin/glucose system. A quasi-parabolic shape was observed when the activity was plotted against alkyl chain length. Additionally, the anti-inflammatory effects of these derivatives were evaluated against methylglyoxal-induced inflammation in RAW264.7 cells. The same trend on anti-inflammatory activity was found as in the antiglycation study. The results showed that tyrosol esters with C12:0 and C14:0 were two most efficient ones among all the tested derivatives. Thus, some lipophilized tyrosol derivatives were stronger antiglycative and anti-inflammatory agents compared to the parent compound, tyrosol.Graphical abstract

Fatty Acid Conjugation Leads to Length-Dependent Antimicrobial Activity of a Synthetic Antibacterial Peptide (Pep19-4LF).

The increasing number of infections caused by multidrug-resistant bacteria requires an intensified search for new antibiotics. Pep19-4LF is a synthetic antimicrobial peptide (GKKYRRFRWKFKGKLFLFG) that was previously designed with the main focus on high antimicrobial activity. The hydrophobic motif, LFLFG, was found to be essential for antimicrobial activity. However, this motif shows several limitations such as aggregation in biological media, low solubility, and small yields in peptide synthesis. In order to obtain more appropriate peptide characteristics, the hydrophobic motif was replaced with fatty acids. For this purpose, a shortened variant of Pep19-4LF (Pep19-short; GKKYRRFRWKFKGK) was synthesized and covalently linked to saturated fatty acids of different chain lengths. The peptide conjugates were tested with respect to their antibacterial activity by microdilution experiments on different bacterial strains. The length of the fatty acid was found to be directly correlated to the antimicrobial activity up to an ideal chain length (undecanoic acid, C11:0). This conjugate showed high antimicrobial activity in absence of toxicity. Time–kill studies revealed a fast and bactericidal mode of action. Furthermore, the first in vivo experiments of the conjugate in rodents demonstrated pharmacokinetics appropriate for application as a drug. These results clearly indicate that the hydrophobic motif of the peptide can be replaced by a single fatty acid of medium length, simplifying the design of this antimicrobial peptide while retaining high antimicrobial activity in the absence of toxicity.