Differential scanning calorimetry in drug-membrane interactions.

Differential Scanning Calorimetry (DSC) is a central technique in investigating drug - membrane interactions, a critical component of pharmaceutical research. DSC measures the heat difference between a sample of interest and a reference as a function of temperature or time, contributing essential knowledge on the thermally induced phase changes in lipid membranes and how these changes are affected by incorporating pharmacological substances. The manuscript discusses the use of phospholipid bilayers, which can form structures like unilamellar and multilamellar vesicles, providing a simplified yet representative membrane model to investigate the complex dynamics of how drugs interact with and penetrate cellular barriers. The manuscript consolidates data from various studies, providing a comprehensive understanding of the mechanisms underlying drug - membrane interactions, the determinants that influence these interactions, and the crucial role of DSC in elucidating these components. It further explores the interactions of specific classes of drugs with phospholipid membranes, including non-steroidal anti-inflammatory drugs, anticancer agents, natural products with antioxidant properties, and Alzheimer's disease therapeutics. The manuscript underscores the critical importance of DSC in this field and the need for continued research to improve our understanding of these interactions, acting as a valuable resource for researchers.

Study of the Membrane Activity of the Synthetic Peptide ∆M3 Against Extended-Spectrum ß-lactamase Escherichia coli Isolates.

Escherichia coli is the most common microorganism causing nosocomial or community-acquired bacteremia, and extended-spectrum ß-lactamase-producing Escherichia coli isolates are identified worldwide with increasing frequency. For this reason, it is necessary to evaluate potential new molecules like antimicrobial peptides. They are recognized for their biological potential which makes them promising candidates in the fight against infections. The goal of this research was to evaluate the potential of the synthetic peptide ΔM3 on several extended-spectrum ß-lactamase producing E. coli isolates. The antimicrobial and cytotoxic activity of the peptide was spectrophotometrically determined. Additionally, the capacity of the peptide to interact with the bacterial membrane was monitored by fluorescence microscopy and infrared spectroscopy. The results demonstrated that the synthetic peptide is active against Escherichia coli isolates at concentrations similar to Meropenem. On the other hand, no cytotoxic effect was observed in HaCaT keratinocyte cells even at 10 times the minimal inhibitory concentration. Microscopy results showed a permeabilizing effect of the peptide on the bacteria. The infrared results showed that ΔM3 showed affinity for the lipids of the microorganism's membrane. The results suggest that the ∆M3 interacts with the negatively charged lipids from the E. coli by a disturbing effect on membrane. Finally, the secondary structure experiments of the peptide showed a random structure in solution that did not change during the interaction with the membranes.

Laser Ablation for the Synthesis of Cu/Cu2O/CuO and Its Development as Photocatalytic Material for Escherichia coli Detoxification.

Advanced Oxidation Processes (AOPs) offer promising methods for disinfection by generating radical species like hydroxyl radicals, superoxide anion radicals, and hydroxy peroxyl, which can induce oxidative stress and deactivate bacterial cells. Photocatalysis, a subset of AOPs, activates a semiconductor using specific electromagnetic wavelengths. A novel material, Cu/Cu2O/CuO nanoparticles (NPs), was synthesized via a laser ablation protocol (using a 1064 nm wavelength laser with water as a solvent, with energy ranges of 25, 50, and 80 mJ for 10 min). The target was sintered from 100 °C to 800 °C at rates of 1.6, 1.1, and 1 °C/min. The composite phases of Cu, CuO, and Cu2O showed enhanced photocatalytic activity under visible-light excitation at 368 nm. The size of Cu/Cu2O/CuO NPs facilitates penetration into microorganisms, thereby improving the disinfection effect. This study contributes to synthesizing mixed copper oxides and exploring their activation as photocatalysts for cleaner surfaces. The electronic and electrochemical properties have potential applications in other fields, such as capacitor materials. The laser ablation method allowed for modification of the band gap absorption and enhancement of the catalytic properties in Cu/Cu2O/CuO NPs compared to precursors. The disinfection of E. coli with Cu/Cu2O/CuO systems serves as a case study demonstrating the methodology's versatility for various applications, including disinfection against different microorganisms, both Gram-positive and Gram-negative.

Staphylococcus aureus Modulates Carotenoid and Phospholipid Content in Response to Oxygen-Restricted Growth Conditions, Triggering Changes in Membrane Biophysical Properties.

Staphylococcus aureus membranes contain carotenoids formed during the biosynthesis of staphyloxanthin. These carotenoids are considered virulence factors due to their activity as scavengers of reactive oxygen species and as inhibitors of antimicrobial peptides. Here, we show that the growth of S. aureus under oxygen-restricting conditions downregulates carotenoid biosynthesis and modifies phospholipid content in biofilms and planktonic cells analyzed using LC-MS. At oxygen-restrictive levels, the staphyloxanthin precursor 4,4-diapophytofluene accumulates, indicating that the dehydrogenation reaction catalyzed by 4,4'-diapophytoene desaturases (CrtN) is inhibited. An increase in lysyl-phosphatidylglycerol is observed under oxygen-restrictive conditions in planktonic cells, and high levels of cardiolipin are detected in biofilms compared to planktonic cells. Under oxygen-restriction conditions, the biophysical parameters of S. aureus membranes show an increase in lipid headgroup spacing, as measured with Laurdan GP, and decreased bilayer core order, as measured with DPH anisotropy. An increase in the liquid-crystalline to gel phase melting temperature, as measured with FTIR, is also observed. S. aureus membranes are therefore less condensed under oxygen-restriction conditions at 37 °C. However, the lack of carotenoids leads to a highly ordered gel phase at low temperatures, around 15 °C. Carotenoids are therefore likely to be low in S. aureus found in tissues with low oxygen levels, such as abscesses, leading to altered membrane biophysical properties.

Biophysical Insights into the Antitumoral Activity of Crotalicidin against Breast Cancer Model Membranes.

Bioactive peptides have emerged as promising therapeutic agents with antimicrobial, antifungal, antiparasitic, and, recently, antitumoral properties with a mechanism of action based on membrane destabilization and cell death, often involving a conformational change in the peptide. This biophysical study aims to provide preliminary insights into the membrane-level antitumoral mode of action of crotalicidin, a cationic host defense peptide from rattlesnake venom, toward breast cancer cell lines. The lipid composition of breast cancer cell lines was obtained after lipid extraction and quantification to prepare representative cell membrane models. Membrane-peptide interaction studies were performed using differential scanning calorimetry and Fourier-transform infrared spectroscopy. The outcome evidences the potential antitumoral activity and selectivity of crotalicidin toward breast cancer cell lines and suggests a mechanism initiated by the electrostatic interaction of the peptide with the lipid bilayer surface and posterior conformation change with membrane intercalation between the acyl chains in negatively charged lipid systems. This research provides valuable information that clears up the antitumoral mode of action of crotalicidin.

Understanding the Biophysical Interaction of LTX-315 with Tumoral Model Membranes.

Host defense peptides are found primarily as natural antimicrobial agents among all lifeforms. These peptides and their synthetic derivatives have been extensively studied for their potential use as therapeutic agents. The most accepted mechanism of action of these peptides is related to a nonspecific mechanism associated with their interaction with the negatively charged groups present in membranes, inducing bilayer destabilization and cell death through several routes. Among the most recently reported peptides, LTX-315 has emerged as an important oncolytic peptide that is currently in several clinical trials against different cancer types. However, there is a lack of biophysical studies regarding LTX-315 and its interaction with membranes. This research focuses primarily on the understanding of the molecular bases of LTX-315's interaction with eukaryotic lipids, based on two artificial systems representative of non-tumoral and tumoral membranes. Additionally, the interaction with individual lipids was studied by differential scanning calorimetry and Fourier-transformed infrared spectroscopy. The results showed a strong interaction of LTX-315 with the negatively charged phosphatidylserine. The results are important for understanding and facilitating the design and development of improved peptides with anticancer activity.

Defining Pathological Activities of ALK in Neuroblastoma, a Neural Crest-Derived Cancer.

Neuroblastoma is a common extracranial solid tumour of childhood, responsible for 15% of cancer-related deaths in children. Prognoses vary from spontaneous remission to aggressive disease with extensive metastases, where treatment is challenging. Tumours are thought to arise from sympathoadrenal progenitor cells, which derive from an embryonic cell population called neural crest cells that give rise to diverse cell types, such as facial bone and cartilage, pigmented cells, and neurons. Tumours are found associated with mature derivatives of neural crest, such as the adrenal medulla or paraspinal ganglia. Sympathoadrenal progenitor cells express anaplastic lymphoma kinase (ALK), which encodes a tyrosine kinase receptor that is the most frequently mutated gene in neuroblastoma. Activating mutations in the kinase domain are common in both sporadic and familial cases. The oncogenic role of ALK has been extensively studied, but little is known about its physiological role. Recent studies have implicated ALK in neural crest migration and sympathetic neurogenesis. However, very few downstream targets of ALK have been identified. Here, we describe pathological activation of ALK in the neural crest, which promotes proliferation and migration, while preventing differentiation, thus inducing the onset of neuroblastoma. Understanding the effects of ALK activity on neural crest cells will help find new targets for neuroblastoma treatment.

[An update on parathyroid carcinoma]. / Puesta al día: carcinoma paratiroideo.

Parathyroid carcinoma is a rare malignant disease that presents as a sporadic or familial primary hyperparathyroidism (PHP). The latter is associated with some genetic syndromes. It occurs with equal frequency in both sexes, unlike PHP caused by parathyroid adenoma that is more common in women. It should be suspected in cases of severe hypercalcemia, with high parathyroid hormone levels and a palpable cervical mass. Given the difficulty in distinguishing between parathyroid carcinoma and adenoma prior to the surgery, the diagnosis is often made after parathyroidectomy. The only curative treatment is complete surgical resection with oncologic block resection of the primary tumor to ensure free margins. Adjuvant therapies with chemotherapy or radiation therapy do not modify overall or disease-free survival. Recurrences are common and re-operation of resectable recurrent disease is recommended. The palliative treatment of symptomatic hypercalcemia is crucial in persistent or recurrent disease after surgery since morbidity and mortality are more associated with hypercalcemia than with tumor burden.

Synthetic Peptide ΔM4-Induced Cell Death Associated with Cytoplasmic Membrane Disruption, Mitochondrial Dysfunction and Cell Cycle Arrest in Human Melanoma Cells.

Melanoma is the most dangerous and lethal form of skin cancer, due to its ability to spread to different organs if it is not treated at an early stage. Conventional chemotherapeutics are failing as a result of drug resistance and weak tumor selectivity. Therefore, efforts to evaluate novel molecules for the treatment of skin cancer are necessary. Antimicrobial peptides have become attractive anticancer agents because they execute their biological activity with features such as a high potency of action, a wide range of targets, and high target specificity and selectivity. In the present study, the antiproliferative activity of the synthetic peptide ΔM4 on A375 human melanoma cells and spontaneously immortalized HaCaT human keratinocytes was investigated. The cytotoxic effect of ΔM4 treatment was evaluated through propidium iodide uptake by flow cytometry. The results indicated selective toxicity in A375 cells and, in order to further investigate the mode of action, assays were carried out to evaluate morphological changes, mitochondrial function, and cell cycle progression. The findings indicated that ΔM4 exerts its antitumoral effects by multitarget action, causing cell membrane disruption, a change in the mitochondrial transmembrane potential, an increase of reactive oxygen species, and cell cycle accumulation in S-phase. Further exploration of the peptide may be helpful in the design of novel anticancer peptides.

An in vitro study of the protective effect of caffeic acid on human erythrocytes.

The interaction and protective effect of caffeic acid (CA) on human erythrocytes (RBC) and molecular models of its membrane were studied. The latter consisted of bilayers built up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representative of phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. X-ray diffraction and differential scanning calorimetry results indicated that CA induced structural and thermotropic perturbations in multilayers and vesicles of DMPC. Fluorescence spectroscopy analysis showed that CA increased the fluidity of DMPC vesicles and of human erythrocyte ghosts. Scanning electron microscopy observations displayed that CA induced morphological alterations to RBC from their normal discoid form to echinocytes. The assessment of its protective capacity showed that CA inhibits RBC morphological alterations and lysis induced by HClO. These findings imply that CA molecules were located in the outer monolayer of the erythrocyte membrane, and that this preferential location might effectively protect the red cells from damage caused by oxidizing species.

How Does Comprehensive Care Impact Life of Pediatric Patients With Hemophilia? Results From a Center in a Developing Country.

BACKGROUND: Quality of life (QoL) has been included as a marker of treatment effectiveness in pediatric patients with chronic diseases. We believe that frequent multidisciplinary interventions and patient education could lead to an improvement in QoL. AIMS: Determine the QoL and economic impact of monthly interventions in multidisciplinary treatment. MATERIALS AND METHODS: The Haemo-QoL questionnaire was applied to patients who attended the hemophilia center of the University Hospital "Dr. José Eleuterio González," Monterrey, Mexico, at the time of enrollment and 1 year later. RESULTS: Male patients between 4 and 16 years diagnosed with hemophilia were included. The score results presented are based on Haemo-QoL versions that classify patients by their age group: group 1 (4 to 7 y) and group 2 (8 to 12 y). Statistical significant improvement was observed in the overall score (sociodemographic, psychosocial, etc.) after 1 year of follow-up in both groups (P<0.05). CONCLUSIONS: Impact on the QoL of patients receiving this approach was favorable. Improvement was observed regardless of severity and in those who were already in prophylaxis, suggesting that this type of approach could be causing the improvement. Results support the application of multidisciplinary treatment as the gold standard, and it should be considered in all centers including those with limited resources.

Identification and evaluation of Galleria mellonella peptides with antileishmanial activity.

Leishmaniasis is a neglected disease, World Health Organization (WHO) declared it as high priority worldwide. Colombia is one of the 98 countries in which the disease caused more than 17.000 cases per year. There is a need to explore novel therapies to reduce the side effects of the current treatments. For this reason, this study was aimed to evaluate Galleria mellonella hemolymph for potential peptides with anti-parasitic activity. Larvae were challenged with Leishmania (V) panamensis promastigotes and hemolymph was analyzed using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), reversed-phase chromatography (RP-HPLC), two-dimensional gel electrophoresis and liquid chromatography-mass spectroscopy (LC/MS). The immunological response of Galleria mellonella was followed by SDS-PAGE, immunized hemolymph was fractionated by RP-HPLC where fractions 5 and 11 showed the highest antileishmanial activity. From these fractions 15 spots were isolated by 2D gel electrophoresis and evaluated by LC/MS to identify the peptides present in the spots. After the analysis Moricin-B, Moricin-C4, Cecropin-D and Anionic Peptide 2 were identified due to the immune challenge with Leishmania promastigotes. Anionic peptide 2 and Cecropin-D were synthesized and evaluated for antileishmanial activity. The results showed that Anionic peptide 2 presented more anti-parasitic activity. This study showed for the first time the anti-parasitic potential of peptides derived from hemolymph of Galleria mellonella.

Entropy drives the insertion of ibuprofen into model membranes.

Understanding the migration of exogenous molecules to the interior of cell membranes is of pivotal importance to the design of new drugs and to the improvement of the capabilities of existing ones. This research dissects, from a molecular perspective, using classical molecular dynamics, the thermodynamic factors driving the insertion of ibuprofen into a model phosphatidylcholine membrane in an aqueous environment. We suggest an analysis of the insertion path that focuses on the net resulting force acting on the tertiary drug/water/membrane system; this allows us to understand the opposition that ibuprofen has to overcome as it inserts into the membrane. We provide conclusive evidence that entropy changes, arising from an increase of the number of possible microstates due to structural reorganization of the tertiary system, are the main factor driving this process. Our results allow us to unambiguously rationalize long standing conflicting experimental reports not understood up to now.

Biophysical study of the non-steroidal anti-inflammatory drugs (NSAID) ibuprofen, naproxen and diclofenac with phosphatidylserine bilayer membranes.

Non-steroidal anti-inflammatory drugs (NSAIDs) represent an effective pain treatment option and therefore one of the most sold therapeutic agents worldwide. The study of the molecular interactions responsible for their physiological activity, but also for their side effects, is therefore important. This report presents data on the interaction of the most consumed NSAIDs (ibuprofen, naproxen and diclofenac) with one main phospholipid in eukaryotic cells, dimyristoylphosphatidylserine (DMPS). The applied techniques are Fourier-transform infrared spectroscopy (FTIR), with which in transmission the gel to liquid crystalline phase transition of the acyl chains in the absence and presence of the NSAID are monitored, supplemented by differential scanning calorimetry (DSC) data on the phase transition. FTIR in reflection (ATR, attenuated total reflectance) is applied to record the dependence of the interactions of the NSAID with particular functional groups observed in the DMPS spectrum such as the ester carbonyl and phosphate vibrational bands. With Förster resonance energy transfer (FRET) a possible intercalation of the NSAID into the DMPS liposomes and with isothermal titration calorimetry (ITC) the thermodynamics of the interaction are monitored. The data show that the NSAID react in a particular way with this lipid, but in some parameters the three NSAID clearly differ, with which now a clear picture of the interaction processes is possible.

The increase in positively charged residues in cecropin D-like Galleria mellonella favors its interaction with membrane models that imitate bacterial membranes.

A comparative study of three synthetic peptides, namely neutral Cecropin D-like G. mellonella (WT) and two cationic peptides derived from its sequence, ΔM1 (+5) and ΔM2 (+9) is reported in this work. The influence of charge on the interactions between peptides and membranes and its effect on phase were studied by calorimetric assays. Differential scanning calorimetry (DSC) showed that ΔM2 peptide showed the strongest effect when the membrane contained phosphatidylcholine (PC) and phosphatidylglycerol (PG), increasing membrane fluidization. Fourier transform infrared spectroscopy (FTIR) was used to determine lipid segregation in the presence of peptides. When WT and ΔM1 bound to model membrane containing PG and PC (1:1 molar ratio) a separation of both lipids was observed. Meanwhile, ΔM2 peptide also induced a demixing of PG-peptide rich domains separated from PC. FTIR experiments also suggested that the presence of ΔM1 and ΔM2 peptides increased lipid carbonyl group hydration in DMPG membrane fluid phase, However, hydration at the interface level in fluid phase was notably increased in the presence of WT and ΔM1 peptides in DMPC/DMPG. Overall the increase in positively charged residues favors the interaction of the peptides with the negatively charged membrane and its perturbation.

Morphological Effects and Antioxidant Capacity of Solanum crispum (Natre) In Vitro Assayed on Human Erythrocytes.

In order to gain insight into the molecular mechanism of the antioxidant properties of Solanum crispum, aqueous extracts of its leaves were assayed on human erythrocytes and molecular models of its membrane. Phenolics and alkaloids were detected by HPLC-MS. Scanning electron and defocusing microscopy showed that S. crispum changed erythrocytes from the normal shape to echinocytes. These results imply that molecules present in the aqueous extracts were located in the outer monolayer of the erythrocyte membrane. Dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were chosen as representative of phospholipid classes located in the outer and inner monolayers of the erythrocyte membrane, respectively. X-ray diffraction showed that S. crispum preferentially interacted with DMPC bilayers. Experiments regarding its antioxidant properties showed that S. crispum neutralized the oxidative capacity of HClO on DMPE bilayers; defocusing microscopy and hemolysis assays demonstrated the protective effect of S. crispum against the oxidant effects of HClO on human erythrocytes.

Antioxidant Capacity of Gallic Acid in vitro Assayed on Human Erythrocytes.

Gallic acid (GA) is a polyphenol present in many plants. This study was aimed to investigate the molecular interaction of GA with the human erythrocyte membrane and to determine its antioxidant capacity. The molecular interaction with the membrane of human red cells and the antioxidant property was assayed on both human red cells and molecular models of its membrane. Observations by optical, scanning electron, and defocusing microscopy demonstrated that GA is capable to convert red cells from their normal biconcave shape to crenated echinocytes. This result indicates that GA molecules are positioned in the outer monolayer of the red cell membrane. Dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were selected as classes of phospholipids found in the outer and inner monolayers of the red cell membrane, respectively. X-ray diffraction and differential scanning calorimetry showed that GA was preferentially bound to DMPC bilayers. Experiments related to the antioxidant capacity of GA indicated that this compound offsets HClO oxidative capacity on DMPE bilayers. In addition, optical, scanning, defocusing microscopy, and hemolysis assays confirmed the protective capacity of GA against HClO deleterious effects on human red cells. As a conclusion, GA would be capable to block the access of oxidants into the lipid bilayer, and thus avoid their access into red cells.

Structural effects of the Solanum steroids solasodine, diosgenin and solanine on human erythrocytes and molecular models of eukaryotic membranes.

This report presents evidence that the following Solanum steroids: solasodine, diosgenin and solanine interact with human erythrocytes and molecular models of their membranes as follows: a) X-ray diffraction studies showed that the compounds at low molar ratios (0.1-10.0mol%) induced increasing structural perturbation to dimyristoylphosphatidylcholine bilayers and to a considerable lower extent to those of dimyristoylphosphatidylethanolamine; b) differential scanning calorimetry data showed that the compounds were able to alter the cooperativity of dimyristoylphosphatidylcholine, dimyristoylphosphatidylethanolamine and dimyristoylphosphatidylserine phase transitions in a concentration-dependent manner; c) in the presence of steroids, the fluorescence of Merocyanine 540 incorporated to the membranes decreased suggesting a fluidization of the lipid system; d) scanning electron microscopy observations showed that all steroids altered the normal shape of human erythrocytes inducing mainly echinocytosis, characterized by the formation of blebs in their surfaces, an indication that their molecules are located into the outer monolayer of the erythrocyte membrane.

Galleria mellonella native and analogue peptides Gm1 and ΔGm1. II) anti-bacterial and anti-endotoxic effects.

Antimicrobial peptides (AMPs) are important components of the innate immune system of animals, plants, fungi and bacteria and are recently under discussion as promising alternatives to conventional antibiotics. We have investigated two cecropin-like synthetic peptides, Gm1, which corresponds to the natural overall uncharged Galleria mellonella native peptide and ΔGm1, a modified overall positively charged Gm1 variant. We have analysed these peptides for their potential to inhibit the endotoxin-induced secretion of tumour necrosis factor-α (TNF-α) from human mononuclear cells. Furthermore, in a conventional microbiological assay, the ability of these peptides to inhibit the growth of the rough mutant bacteria Salmonella enterica Minnesota R60 and the polymyxin B-resistant Proteus mirabilis R45 was investigated and atomic force microscopy (AFM) measurements were performed to characterize the morphology of the bacteria treated by the two peptides. We have also studied their cytotoxic properties in a haemolysis assay to clarify potential toxic effects. Our data revealed for both peptides minor anti-inflammatory (anti-endotoxin) activity, but demonstrated antimicrobial activity with differences depending on the endotoxin composition of the respective bacteria. In accordance with the antimicrobial assay, AFM data revealed a stronger morphology change of the R45 bacteria than for the R60. Furthermore, Gm1 had a stronger effect on the bacteria than ΔGm1, leading to a different morphology regarding indentations and coalescing of bacterial structures. The findings verify the biophysical measurements with the peptides on model systems. Both peptides lack any haemolytic activity up to an amount of 100µg/ml, making them suitable as new anti-infective agents.

Galleria mellonella native and analogue peptides Gm1 and ΔGm1. I) biophysical characterization of the interaction mechanisms with bacterial model membranes.

Natural occurring antimicrobial peptides (AMPs) are important components of the innate immune system of animals and plants. They are considered to be promising alternatives to conventional antibiotics. Here we present a comparative study of two synthetic peptides: Gm1, corresponding to the natural overall uncharged peptide from Galleria mellonella (Gm) and ΔGm1, a modified overall positively charged Gm1 variant. We have studied the interaction of the peptides with lipid membranes composed of different kinds of lipopolysaccharides (LPS) and dimyristoylphosphatidylglycerol (DMPG), in some cases also dimyristoylphosphatidylethanolamine (DMPE) as representative lipid components of Gram-negative bacterial membranes, by applying Fourier-transform infrared spectroscopy (FTIR), Förster resonance energy transfer spectroscopy (FRET), differential scanning calorimetry (DSC) and isothermal titration calorimetry (ITC). Gm1 generates a destabilizing effect on the gel to liquid crystalline phase transition of the acyl chains of the lipids, as deduced from a decrease in the phase transition temperature and enthalpy, suggesting a fluidization, whereas ΔGm1 led to the opposite behavior. Further, FTIR analysis of the functional groups of the lipids participating in the interaction with the peptides indicated a shift in the band position and intensity of the asymmetric PO2(-) stretching vibration originating from the lipid phosphate groups, a consequence of the sterical changes in the head group region. Interestingly, FRET spectroscopy showed a similar intercalation of both peptides into the DMPG and LPS, but much less into the DMPE membrane systems. These results are discussed in the light of a possible use of the peptides as antimicrobial and anti-endotoxin drugs.