Vibrational Analysis of Amino Acids and Short Peptides in Hydrated Media. VIII. Amino Acids with Aromatic Side Chains: l-Phenylalanine, l-Tyrosine, and l-Tryptophan

Structural properties and microbial diversity of the biofilm colonizing plastic substrates in Terra Nova Bay (Antarctica)

Microbial colonization on plastic polymers has been extensively explored, however the temporal dynamics of biofilm community in Antarctic environments are almost unknown. As a contribute to fill this knowledge gap, the structural characteristics and microbial diversity of the biofilm associated with polyvinyl chloride (PVC) and polyethylene (PE) panels submerged at 5 m of depth and collected after 3, 9 and 12 months were investigated in four coastal sites of the Ross Sea. Additional panels placed at 5 and 20 m were retrieved after 12 months. Chemical characterization was performed by FTIR-ATR and Raman (through Surface-Enhanced Raman Scattering, SERS) spectroscopy. Bacterial community composition was quantified at a single cell level by Catalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) and Confocal Laser Scanning Microscopy (CLSM); microbial diversity was assessed by 16S rRNA gene sequencing. This multidisciplinary approach has provided new insights into microbial community dynamics during biofouling process, shedding light on the biofilm diversity and temporal succession on plastic substrates in the Ross Sea. Significant differences between free-living and microbial biofilm communities were found, with a more consolidated and structured community composition on PVC compared to PE. Spectral features ascribable to tyrosine, polysaccharides, nucleic acids and lipids characterized the PVC-associated biofilms. Pseudomonadota (among Gamma-proteobacteria) and Alpha-proteobacteria dominated the microbial biofilm community. Interestingly, in Road Bay, close to the Italian "Mario Zucchelli" research station, the biofilm growth - already observed during summer season, after 3 months of submersion - continued afterwards leading to a massive microbial abundance at the end of winter (after 12 months). After 3 months, higher percentages of Gamma-proteobacteria in Road Bay than in the not-impacted site were found. These observations lead us to hypothesize that in this site microbial fouling developed during the first 3 months could serve as a starter pioneering community stimulating the successive growth during winter.

Relationships between conformational and vibrational features of tryptophan characteristic Raman markers

Tryptophan (Trp) residue provides characteristic vibrational markers to the middle wavenumber spectral region of the Raman spectra recorded from peptides and proteins. In this report, we were particularly interested in eight Trp Raman markers, referred to as Wi (i = 1,…,8). All responsible for pronounced Raman lines, these markers originate from indole moiety, a bicyclic conjugated segment involved in the Trp structure. Numerous investigations have previously attempted to relate the variations observed in the spectral features of these markers to the environmental changes of Trp residues. To emphasize the most important points we can mention (i) the variations in the Raman profile of W4 (∼1360 cm-1) and W5 (∼1340 cm-1), frequently observed as a doublet with variable intensity ratio. These two markers were thought to result from a Fermi-resonance effect between certain planar and nonplanar modes; (ii) the changes observed in the wavenumbers and relative intensities of W4, W7 (∼880 cm-1) and W8 (∼760 cm-1) were supposed to be related to the accessibility of Trp to surrounding water molecules; and (iii) the wavenumber fluctuations of W3 (∼1550 cm-1), taken as a Trp side chain orientational marker. However, some ambiguities still exist regarding the interpretation of these markers, needing further clarification. Herein, upon a joint experimental and theoretical analysis based on a multiconformational approach, attention was paid to the relationships between structural and vibrational features of three indole-containing compounds with increasing structural complexity, i.e., skatole (3-methylindole), tryptophan, and tripeptide Gly-Trp-Gly. This study clearly shows that the existing assignments given to certain Trp Raman markers should be reconsidered, especially those based on the Fermi-resonance origin of W4-W5 (∼1360-1340 cm-1) doublet, as well as the purely environmental dependence of W7 and W8 markers.

Multi-Wavelength Raman Differentiation of Malignant Skin Neoplasms

Raman microspectroscopy has become an effective method for analyzing the molecular appearance of biomarkers in skin tissue. For the first time, we acquired in vitro Raman spectra of healthy and malignant skin tissues, including basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), at 532 and 785 nm laser excitation wavelengths in the wavenumber ranges of 900-1800 cm-1 and 2800-3100 cm-1 and analyzed them to find spectral features for differentiation between the three classes of the samples. The intensity ratios of the bands at 1268, 1336, and 1445 cm-1 appeared to be the most reliable criteria for the three-class differentiation at 532 nm excitation, whereas the bands from the higher wavenumber region (2850, 2880, and 2930 cm-1) were a robust measure of the increased protein/lipid ratio in the tumors at both excitation wavelengths. Selecting ratios of the three bands from the merged (532 + 785) dataset made it possible to increase the accuracy to 87% for the three classes and reach the specificities for BCC + SCC equal to 87% and 81% for the sensitivities of 95% and 99%, respectively. Development of multi-wavelength excitation Raman spectroscopic techniques provides a versatile non-invasive tool for research of the processes in malignant skin tumors, as well as other forms of cancer.

The relationship between the tyrosine residue 850-830 cm-1 Raman doublet intensity ratio and the aromatic side chain χ1 torsion angle

Tyrosine (Tyr) residue in a peptide chain is characterized by the presence of seven Raman markers, referred to as Yi (i = 1, …, 7), distributed over the middle wavenumber spectral region. Particularly, the changes observed in the relative intensity of Y5 and Y6 markers, appearing as a side by side doublet at ca. 850-830 cm-1, has received a great attention. Primarily assigned to a Fermi-resonance effect between phenol ring planar and nonplanar modes, former density functional theory calculations led us to affiliate the Y5-Y6 doublet to two distinct fundamental modes. Furthermore, despite the previous assumptions, it was evidenced that the reversal of the doublet intensity ratio cannot be solely explained by hydrogen bonding on the phenol hydroxyl group involved in Tyr. Herein, upon analyzing the observed and theoretical data collected from the cationic species of the tripeptide Gly-Tyr-Gly, the crucial effect of the aromatic side chain orientation, especially that of the χ1 torsion angle defined around the CαCβ bond, on the Tyr doublet intensity ratio has been evidenced.

Streamlined Multi-Attribute Assessment of an Array of Clinical-Stage Antibodies: Relationship Between Degradation and Stability

Clinical antibodies are an important class of drugs for the treatment of both chronic and acute diseases. Their manufacturability is subject to evaluation to ensure product quality and efficacy. One critical quality attribute is deamidation, a non-enzymatic process that is observed to occur during thermal stress, at low or high pH, or a combination thereof. Deamidation may induce antibody instability and lead to aggregation, which may pose immunogenicity concerns. The introduction of a negative charge via deamidation may impact the desired therapeutic function (i) within the complementarity-determining region, potentially causing loss of efficacy; or (ii) within the fragment crystallizable region, limiting the effector function involving antibody-dependent cellular cytotoxicity. Here we describe a transformative solution that allows for a comparative assessment of deamidation and its impact on stability and aggregation. The innovative streamlined method evaluates the intact protein in its formulation conditions. This breakthrough platform technology is comprised of a quantum cascade laser microscope, a slide cell array that allows for flexibility in the design of experiments, and dedicated software. The enhanced spectral resolution is achieved using two-dimensional correlation, co-distribution, and two-trace two-dimensional correlation spectroscopies that reveal the molecular impact of deamidation. Eight re-engineered immunoglobulin G4 scaffold clinical antibodies under control and forced degradation conditions were evaluated for deamidation and aggregation. We determined the site of deamidation, the overall extent of deamidation, and where applicable, whether the deamidation event led to self-association or aggregation of the clinical antibody and the molecular events that led to the instability. The results were confirmed using orthogonal techniques for four of the samples.

Raman spectroscopy and Raman optical activity of blood plasma for differential diagnosis of gastrointestinal cancers

Improving the early diagnosis of gastrointestinal cancers is a crucial step in reducing their mortality. Given the non-specificity of the initial symptoms, the ability of any diagnostic method to differentiate between various types of gastrointestinal cancers also needs to be addressed. To detect disease-specific alterations in biomolecular structure and composition of the blood plasma, we have implemented an approach combining Raman spectroscopy and its conformation-sensitive polarized version, Raman optical activity, to analyze blood plasma samples of patients suffering from three different types of gastrointestinal cancer - hepatocellular, colorectal and pancreatic. First, we aimed to discriminate any type of gastrointestinal cancer from healthy control individuals; inthenext step, the focus was on differentiating among the three cancer types studied. The more straightforward of the two statistical approaches tested, the combination of linear discriminant analysis and principal component analysis applied to the entire spectral dataset, allowed the discrimination of cancer and control samples with 87% accuracy. The three gastrointestinal cancers were classified with an overall accuracy of 76%. The second method, the linear discriminant analysis applied to a selection of spectral bands, yielded even higher values. Cancer and control samples were distinguished with 89% accuracy and hepatocellular, colorectal and pancreatic cancer with an overall accuracy of 87%. The results obtained in our study suggest that the proposed approach may become a disease-specific diagnostic tool in daily clinical practice.

Raman Fingerprints of SARS-CoV-2 Omicron Subvariants: Molecular Roots of Virological Characteristics and Evolutionary Directions

The latest RNA genomic mutation of SARS-CoV-2 virus, termed the Omicron variant, has generated a stream of highly contagious and antibody-resistant strains, which in turn led to classifying Omicron as a variant of concern. We systematically collected Raman spectra from six Omicron subvariants available in Japan (i.e., BA.1.18, BA.2, BA.4, BA.5, XE, and BA.2.75) and applied machine-learning algorithms to decrypt their structural characteristics at the molecular scale. Unique Raman fingerprints of sulfur-containing amino acid rotamers, RNA purines and pyrimidines, tyrosine phenol ring configurations, and secondary protein structures clearly differentiated the six Omicron subvariants. These spectral characteristics, which were linked to infectiousness, transmissibility, and propensity for immune evasion, revealed evolutionary motifs to be compared with the outputs of genomic studies. The availability of a Raman "metabolomic snapshot", which was then translated into a barcode to enable a prompt subvariant identification, opened the way to rationalize in real-time SARS-CoV-2 activity and variability. As a proof of concept, we applied the Raman barcode procedure to a nasal swab sample retrieved from a SARS-CoV-2 patient and identified its Omicron subvariant by coupling a commercially available magnetic bead technology with our newly developed Raman analyses.

Raman spectroscopy and mass spectrometry identifies a unique group of epidermal lipids in active discoid lupus erythematosus

Discoid lupus erythematosus (DLE) is the most common form of cutaneous lupus1. It can cause permanent scarring. The pathophysiology of is not fully understood. Plasmacytoid dendritic cells are found in close association with apoptotic keratinocytes inferring close cellular signalling. Matrix Associated Laser Desorption Ionisation (MALDI) combined with Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS) is an exquisitely sensitive combination to examine disease processes at the cellular and molecular level. Active areas of discoid lupus erythematosus were compared with normal perilesional skin using MALDI combined with FT-ICR-MS. A unique set of biomarkers, including epidermal lipids is identified in active discoid lupus. These were assigned as sphingomyelins, phospholipids and ceramides. Additionally, increased levels of proteins from the keratin, and small proline rich family, and aromatic amino acids (tryptophan, phenylalanine, and tyrosine) in the epidermis are observed. These techniques, applied to punch biopsies of the skin, have shown a distinctive lipid profile of active discoid lupus. This profile may indicate specific lipid signalling pathways. Lipid rich microdomains (known as lipid rafts) are involved in cell signalling and lipid abnormalities have been described with systemic lupus erythematosus which correlate with disease activity.

Aromatic Zipper Topology Dictates Water-Responsive Actuation in Phenylalanine-Based Crystals

Water-responsive (WR) materials that reversibly deform in response to relative humidity (RH) changes are gaining increasing interest for their potential in energy harvesting and soft robotics applications. Despite progress, there are significant gaps in the understanding of how supramolecular structure underpins the reconfiguration and performance of WR materials. Here, three crystals are compared based on the amino acid phenylalanine (F) that contain water channels and F packing domains that are either layered (F), continuously connected (phenylalanyl-phenylalanine, FF), or isolated (histidyl-tyrosyl-phenylalanine, HYF). Hydration-induced reconfiguration is analyzed through changes in hydrogen-bond interactions and aromatic zipper topology. F crystals show the greatest WR deformation (WR energy density of 19.8 MJ m^-3 ) followed by HYF (6.5 MJ m^-3 ), while FF exhibits no observable response. The difference in water-responsiveness strongly correlates to the deformability of aromatic regions, with FF crystals being too stiff to deform, whereas HYF is too soft to efficiently transfer water tension to external loads.  These findings reveal aromatic topology design rules for WR crystals and provide insight into general mechanisms of high-performance WR actuation. Moreover, the best-performing crystal, F emerges as an efficient WR material for applications at scale and low cost.

Historical Silk: A Novel Method to Evaluate Degumming with Non-Invasive Infrared Spectroscopy and Spectral Deconvolution

To correctly manage a collection of historical silks, it is important to detect if the yarn has been originally subjected to degumming. This process is generally applied to eliminate sericin; the obtained fiber is named soft silk, in contrast with hard silk which is unprocessed. The distinction between hard and soft silk gives both historical information and useful indications for informed conservation. With this aim, 32 samples of silk textiles from traditional Japanese samurai armors (15th-20th century) were characterized in a non-invasive way. ATR-FTIR spectroscopy has been previously used to detect hard silk, but data interpretation is challenging. To overcome this difficulty, an innovative analytical protocol based on external reflection FTIR (ER-FTIR) spectroscopy was employed, coupled with spectral deconvolution and multivariate data analysis. The ER-FTIR technique is rapid, portable, and widely employed in the cultural heritage field, but rarely applied to the study of textiles. The ER-FTIR band assignment for silk was discussed for the first time. Then, the evaluation of the OH stretching signals allowed for a reliable distinction between hard and soft silk. Such an innovative point of view, which exploits a "weakness" of FTIR spectroscopy-the strong absorption from water molecules-to indirectly obtain the results, can have industrial applications too.

Identification of metal-sensitive structural changes in the Ca2+-binding photocomplex from Thermochromatium tepidum by isotope-edited vibrational spectroscopy

Calcium ions play a dual role in expanding the spectral diversity and structural stability of photocomplexes from several Ca2+-requiring purple sulfur phototrophic bacteria. Here, metal-sensitive structural changes in the isotopically labeled light-harvesting 1 reaction center (LH1-RC) complexes from the thermophilic purple sulfur bacterium Thermochromatium ( Tch.) tepidum were investigated by perfusion-induced attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy. The ATR-FTIR difference spectra induced by exchanges between native Ca2+ and exogenous Ba2+ exhibited interconvertible structural and/or conformational changes in the metal binding sites at the LH1 C-terminal region. Most of the characteristic Ba2+/Ca2+ difference bands were detected even when only Ca ions were removed from the LH1-RC complexes, strongly indicating the pivotal roles of Ca2+ in maintaining the LH1-RC structure of Tch. tepidum. Upon 15N-, 13C- or 2H-labeling, the LH1-RC complexes exhibited characteristic 15N/14N-, 13C/12C-, or 2H/1H-isotopic shifts for the Ba2+/Ca2+ difference bands. Some of the 15N/14N or 13C/12C bands were also sensitive to further 2H-labelings. Given the band frequencies and their isotopic shifts along with the structural information of the Tch. tepidum LH1-RC complexes, metal-sensitive FTIR bands were tentatively identified to the vibrational modes of the polypeptide main chains and side chains comprising the metal binding sites. Furthermore, important new IR marker bands highly sensitive to the LH1 BChl a conformation in the Ca2+-bound states were revealed based on both ATR-FTIR and near-infrared Raman analyses. The present approach provides valuable insights concerning the dynamic equilibrium between the Ca2+- and Ba2+-bound states statically resolved by x-ray crystallography.

Fano resonance line shapes in the Raman spectra of tubulin and microtubules reveal quantum effects

Microtubules are self-assembling biological nanotubes made of the protein tubulin that are essential for cell motility, cell architecture, cell division, and intracellular trafficking. They demonstrate unique mechanical properties of high resilience and stiffness due to their quasi-crystalline helical structure. It has been theorized that this hollow molecular nanostructure may function like a quantum wire where optical transitions can take place, and photoinduced changes in microtubule architecture may be mediated via changes in disulfide or peptide bonds or stimulated by photoexcitation of tryptophan, tyrosine, or phenylalanine groups, resulting in subtle protein structural changes owing to alterations in aromatic flexibility. Here, we measured the Raman spectra of a microtubule and its constituent protein tubulin both in dry powdered form and in aqueous solution to determine if molecular bond vibrations show potential Fano resonances, which are indicative of quantum coupling between discrete phonon vibrational states and continuous excitonic many-body spectra. The key findings of this work are that we observed the Raman spectra of tubulin and microtubules and found line shapes characteristic of Fano resonances attributed to aromatic amino acids and disulfide bonds.

Ex Vivo Vibration Spectroscopic Analysis of Colorectal Polyps for the Early Diagnosis of Colorectal Carcinoma

Colorectal cancer is one of the most common and often fatal cancers in humans, but it has the highest chance of a cure if detected at an early precancerous stage. Carcinogenesis in the colon begins as an uncontrolled growth forming polyps. Some of these polyps can finally be converted to colon cancer. Early diagnosis of adenomatous polyps is the main approach for screening and preventing colorectal cancer, and vibration spectroscopy can be used for this purpose. This work is focused on evaluating FTIR and Raman spectroscopy as a tool in the ex vivo analysis of colorectal polyps, which could be important for the early diagnosis of colorectal carcinoma. Multivariate analyses (PCA and LDA) were used to assist the spectroscopic discrimination of normal colon tissue, as well as benign and malignant colon polyps. The spectra demonstrated evident differences in the characteristic bands of the main tissue constituents, i.e., proteins, nucleic acids, lipids, polysaccharides, etc. Suitable models for discriminating the three mentioned diagnostic groups were proposed based on multivariate analyses of the spectroscopic data. LDA classification was especially successful in the case of a combined set of 55 variables from the FTIR, FT Raman and dispersion Raman spectra. This model can be proposed for ex vivo colorectal cancer diagnostics in combination with the colonoscopic extraction of colon polyps for further testing. This pilot study is a precursor for the further evaluation of the diagnostic potential for the simultaneous in vivo application of colonoscopic Raman probes.

Spectroscopic Investigations of 316L Stainless Steel under Simulated Inflammatory Conditions for Implant Applications: The Effect of Tryptophan as Corrosion Inhibitor/Hydrophobicity Marker

In this paper, the conformational changes of tryptophan (Trp) on the corroded 316 L stainless steel (SS) surface obtained under controlled simulated inflammatory conditions have been studied by Raman (RS) and Fourier-transform infrared (FT-IR) spectroscopy methods. The corrosion behavior and protective efficiency of the investigated samples were performed using the potentiodynamic polarization (PDP) technique in phosphate-buffered saline (PBS) solution acidified to pH 3.0 at 37 °C in the presence and absence of 10−2 M Trp, with different immersion times (2 h and 24 h). The amino acid is adsorbed onto the corroded SS surface mainly through the lone electron pair of the nitrogen atom of the indole ring, which adopts a more/less tilted orientation, and the protonated amine group. The visible differences in the intensity of the Fermi doublet upon adsorption of Trp onto the corroded SS surface, which is a sensitive marker of the local environment, suggested that a stronger hydrophobic environment is observed. This may result in an improvement of the corrosion resistance, after 2 h than 24 h of exposure time. The electrochemical results confirm this statement—the inhibition efficiency of Trp, acting as a mixed-type inhibitor, is made drastically higher after a short period of immersion.

Bioinformatics methods for identification of amyloidogenic peptides show robustness to misannotated training data

Several disorders are related to amyloid aggregation of proteins, for example Alzheimer's or Parkinson's diseases. Amyloid proteins form fibrils of aggregated beta structures. This is preceded by formation of oligomers-the most cytotoxic species. Determining amyloidogenicity is tedious and costly. The most reliable identification of amyloids is obtained with high resolution microscopies, such as electron microscopy or atomic force microscopy (AFM). More frequently, less expensive and faster methods are used, especially infrared (IR) spectroscopy or Thioflavin T staining. Different experimental methods are not always concurrent, especially when amyloid peptides do not readily form fibrils but oligomers. This may lead to peptide misclassification and mislabeling. Several bioinformatics methods have been proposed for in-silico identification of amyloids, many of them based on machine learning. The effectiveness of these methods heavily depends on accurate annotation of the reference training data obtained from in-vitro experiments. We study how robust are bioinformatics methods to weak supervision, encountering imperfect training data. AmyloGram and three other amyloid predictors were applied. The results proved that a certain degree of misannotation in the reference data can be eliminated by the bioinformatics tools, even if they belonged to their training set. The computational results are supported by new experiments with IR and AFM methods.

Miscibility characterization of zein/methacrylic acid copolymer composite films and plasticization effects

Composite films have gained interest for producing films with optimal properties, without the need of chemical modification. Miscibility of components in the film is important for attaining reproducible and consistent film properties. This study used several techniques, i.e. differential scanning calorimetry, Fourier transform infrared spectroscopy and Raman spectroscopy to understand the degree of miscibility of components and its impact on morphology and mechanical properties of the composite film prepared by casting the blend of zein and methacrylic acid copolymer (Eudragit® L100-55). The effects of composition and plasticization by triethyl citrate and polyethylene glycol 1000 were explored. The results demonstrate the miscibility of zein and methacrylic acid copolymer at a molecular level; and the phase behavior of polymer blends is modified by plasticization. Polyethylene glycol 1000 is more compatible with the polymer blend. Its plasticization effect is associated with an increase in β-sheets. Understanding the miscibility between the plasticizer and the polymer blend allows the ability to predict and control mechanical properties of the zein/methacrylic acid copolymer composite film, in particular when the plasticizer level is changed.

Amino acid side chain contribution to protein FTIR spectra: impact on secondary structure evaluation

Prediction of protein secondary structure from FTIR spectra usually relies on the absorbance in the amide I–amide II region of the spectrum. It assumes that the absorbance in this spectral region, i.e., roughly 1700–1500 cm⁻¹ is solely arising from amide contributions. Yet, it is accepted that, on the average, about 20% of the absorbance is due to amino acid side chains. The present paper evaluates the contribution of amino acid side chains in this spectral region and the potential to improve secondary structure prediction after correcting for their contribution. We show that the β-sheet content prediction is improved upon subtraction of amino acid side chain contributions in the amide I–amide II spectral range. Improvement is relatively important, for instance, the error of prediction of β-sheet content decreases from 5.42 to 4.97% when evaluated by ascending stepwise regression. Other methods tested such as partial least square regression and support vector machine have also improved accuracy for β-sheet content evaluation. The other structures such as α-helix do not significantly benefit from side chain contribution subtraction, in some cases prediction is even degraded. We show that co-linearity between secondary structure content and amino acid composition is not a main limitation for improving secondary structure prediction. We also show that, even though based on different criteria, secondary structures defined by DSSP and XTLSSTR both arrive at the same conclusion: only the β-sheet structure clearly benefits from side chain subtraction. It must be concluded that side chain contribution subtraction benefit for the evaluation of other secondary structure contents is limited by the very rough description of side chain absorbance which does not take into account the variations related to their environment. The study was performed on a large protein set. To deal with the large number of proteins present, we worked on protein microarrays deposited on BaF₂ slides and FTIR spectra were acquired with an imaging system.

Evaluation of aromatic amino acids as potential biomarkers in breast cancer by Raman spectroscopy analysis

The scope of the work undertaken in this paper was to explore the feasibility and reliability of using the Raman signature of aromatic amino acids as a marker in the detection of the presence of breast cancer and perhaps, even the prediction of cancer development in very early stages of cancer onset. To be able to assess this hypothesis, we collected most recent and relevant literature in which Raman spectroscopy was used as an analytical tool in the evaluation of breast cell lines and breast tissue, re-analyzed all the Raman spectra, and extracted all spectral bands from each spectrum that were indicative of aromatic amino acids. The criteria for the consideration of the various papers for this study, and hence, the inclusion of the data that they contained were two-fold: (1) The papers had to focus on the characterization of breast tissue with Raman spectroscopy, and (2) the spectra provided within these papers included the spectral range of 500-1200 cm-1, which constitutes the characteristic region for aromatic amino acid vibrational modes. After all the papers that satisfied these criteria were collected, the relevant spectra from each paper were extracted, processed, normalized. All data were then plotted without bias in order to decide whether there is a pattern that can shed light on a possible diagnostic classification. Remarkably, we have been able to demonstrate that cancerous breast tissues and cells decidedly exhibit overexpression of aromatic amino acids and that the difference between the extent of their presence in cancerous cells and healthy cells is overwhelming. On the basis of this analysis, we conclude that it is possible to use the signature Raman bands of aromatic amino acids as a biomarker for the detection, evaluation and diagnosis of breast cancer.

SERS-based sensor for direct L-selectin level determination in plasma samples as alternative method of tumor detection

Selectin ligands are present on the surface of tumor cells, for this reason lowering the L-selectin level in the blood and lymph can indicate presence of the tumor. Therefore the selectin level in the plasma are potential targets for anticancer therapy. We demonstrate the surface enhanced Raman spectroscopy (SERS)-based sensor for the determination of L-selectin level in biological samples that can be used in medical diagnosis. The combination of SERS with the method of multivariate analysis as principle component analysis (PCA) allows to strengthen the presented data analysis. The loadings of PCA permit to indicate those vibration modes, that are the most important for the assumed identification (bands at 1574, 1450, 1292 cm^-1 ). Two bands at 1286 and 1580 cm^-1 were selected for the determination of the calibration curve (bands intensities I₁₂₈₆ /I₁₅₈₀ ratio). The L-selectin level of biological samples can be read, directly from the calibration curve. The presented sensor is as a sensitive tool with good specificity and selectivity of L-selectin, even in the case of coexistence of P- and E-selectin.

Reflection Absorption Infrared Spectroscopy Characterization of SAM Formation from 8-Mercapto-N-(phenethyl)octanamide Thiols with Phe Ring and Amide Groups

Multifunctional amide-containing self-assembled monolayers (SAMs) provide prospects for the construction of interfaces with required physicochemical properties and distinctive stability. In this study, we report the synthesis of amide-containing thiols with terminal phenylalanine (Phe) ring functionality (HS(CH₂)₇CONH(CH₂)₂C₆H₅) and the characterization of the formation of SAMs from these thiols on gold by reflection absorption infrared spectroscopy (RAIRS). For reliable assignments of vibrational bands, ring deuterated analogs were synthesized and studied as well. Adsorption time induced changes in Amide-II band frequency and relative intensity of Amide-II/Amide-I bands revealed two-state sigmoidal form dependence with a transition inflection points at 2.2 ± 0.5 and 4.7 ± 0.5 min, respectively. The transition from initial (disordered) to final (hydrogen-bonded, ordered) structure resulted in increased Amide-II frequency from 1548 to 1557 cm^-1, which is diagnostic for a strongly hydrogen-bonded amide network in trans conformation. However, the lateral interactions between the alkyl chains were found to be somewhat reduced when compared with well-ordered alkane thiol monolayers.

Investigation of proteinaceous paint layers, composed of egg yolk and lead white, exposed to fire-related effects

Fires can have a negative impact on the environment, human health, property and ultimately also on various objects of cultural heritage (CH). This paper deals with an investigation into the degradation of selected proteinaceous paint layers that were exposed to fire-related effects (i.e., fire effluents and/or high temperatures) in a modified cone-calorimeter system. Paint layers of egg yolk adhesive (E) and lead white tempera (E + LW) were exposed to fire-related impacts on top of a CH stack and in a specially designed CH test chamber. On the CH stack, the proteinaceous paint layers were exposed to fire effluents and high temperatures, while in the CH test chamber, the samples were exposed mainly to fire effluents. The molecular changes to the exposed paint layers were analysed by invasive and non-invasive spectroscopic analyses (i.e., FTIR and Raman spectroscopy) and complimented with pyrolysis-GC–MS, while the colour changes were evaluated using colourimetry. It was concluded that the proteinaceous binder degrades into aromatic amino acids and/or fatty acids after exposure to the overall impacts of the fire. Aromatic amino acids were detected by means of the FTIR and py-GC–MS analyses. In the case of the lead white tempera exposure, partial dissociation of the lead white pigment was confirmed by the detection of alteration products, such as lead oxide and lead carbonate. Moreover, the investigation of the E + LW samples exposed for longer times revealed the presence of lead carboxylates. On the other hand, no significant molecular changes were observed with the CH samples exposed to fire effluents in the CH test chamber. The research offered us an insight into the fire-induced effects on selected paints for the first time.

Multiconformational analysis of tripeptides upon consideration of implicit and explicit hydration effects

During the last two decades, numerous observed data obtained by various physical techniques, also supported by molecular modeling approaches, have highlighted the structuring features of tripeptides, as well as their aggregation properties. Herein, we focus on the structural dynamics of four trimers, i.e., Gly-Gly-Gly, Gly-Ala-Gly, Ala-Ala-Ala and Ala-Phe-Ala, in an aqueous environment. Density functional theory calculations (DFT) were carried out to assess the stability of four types of secondary structures, i.e., β-strand, polyproline-II (pP-II), α-helix and γ-turn, of which the formation had been described in these tripeptides. Both implicit and explicit hydration effects were analyzed on the conformational and energetic features of trimers. It has been shown that the use of M062X functional (versus B3LYP) improve the stability of intramolecular H-bonds, especially in inverse γ-turn structures, as well as the energetic and conformational equilibrium in all tripeptides. Explicit hydration reflected by the presence of five water molecules around the backbone polar sites (NH₃⁺, N-H, CO and NH₂) considerably changes the conformational landscapes of the trimers. Characteristic intramolecular and intermolecular interactions evidenced by the calculations, were emphasized.

Zinc Oxide Nanocomposites-Extracellular Synthesis, Physicochemical Characterization and Antibacterial Potential

This research presents, for the first time, the potential of the Lactobacillus paracasei LC20 isolated from sweet whey as a novel, effective and accessible source for post-cultured ZnO nanocomposites synthesis. The obtained nanocomposites were subjected to comprehensive characterization by a broad spectrum of instrumental techniques. Results of spectroscopic and microscopic analysis confirmed the hexagonal crystalline structure of ZnO in the nanometer size. The dispersion stability of the obtained nanocomposites was determined based on the zeta potential (ZP) measurements-the average ZP value was found to be -29.15 ± 1.05 mV in the 7-9 pH range. The ZnO nanocomposites (NCs) demonstrated thermal stability up to 130 °C based on the results of thermogravimetric TGA/DTG) analysis. The organic deposit on the nanoparticle surface was recorded by spectroscopic analysis in the infrared range (FT-IR). Results of the spectrometric study exhibited nanostructure-assisted laser desorption/ionization effects and also pointed out the presence of organic deposits and, what is more, allowed us to identify the specific amino acids and peptides present on the ZnO NCs surfaces. In this context, mass spectrometry (MS) data confirmed the nano-ZnO formation mechanism. Moreover, fluorescence data showed an increase in fluorescence signal in the presence of nanocomposites designed for potential use as, e.g., biosensors. Despite ZnO NCs' luminescent properties, they can also act as promising antiseptic agents against clinically relevant pathogens. Therefore, a pilot study on the antibacterial activity of biologically synthesized ZnO NCs was carried out against four strains (Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae and Pseudomonas aeruginosa) by using MIC (minimal inhibitory concentration). Additionally, the colony forming units (CFU) assay was performed and quantified for all bacterial cells as the percentage of viable cells in comparison to a control sample (untreated culture) The nanocomposites were effective among three pathogens with MIC values in the range of 86.25-172.5 μg/mL and showed potential as a new type of, e.g., medical path or ointment formulation.

Structural Analysis of Nonapeptides Derived from Elastin

Elastin-derived peptides are released from the extracellular matrix remodeling by numerous proteases and seem to regulate many biological processes, notably cancer progression. The canonical elastin peptide is VGVAPG, which harbors the XGXXPG consensus pattern, allowing interaction with the elastin receptor complex located at the surface of cells. Besides these elastokines, another class of peptides has been identified. This group of bioactive elastin peptides presents the XGXPGXGXG consensus sequence, but the reason for their bioactivity remains unexplained. To better understand their nature and structure-function relationships, herein we searched the current databases for this nonapeptide motif and observed that the XGXPGXGXG elastin peptides define a specific group of tandemly repeated patterns. Further, we focused on four tandemly repeated human elastin nonapeptides, i.e., AGIPGLGVG, VGVPGLGVG, AGVPGLGVG, and AGVPGFGAG. These peptides were analyzed by means of optical spectroscopies and molecular dynamics. Ultraviolet-circular dichroism and Raman spectra are consistent with a mixture of β-turn, β-strand, and random-chain secondary elements in aqueous media. Quantitative analysis of their conformations suggested that turns corresponded to half of the total population of structural elements, whereas the remaining half were equally distributed between β-strand and unordered chains. These distributions were confirmed by molecular dynamics simulations. Altogether, our data suggest that these highly dynamic peptides harbor a type II β-turn located in their central part. We hypothesize that this structural element could explain their specific bioactivity.

The FT-IR and Raman Spectroscopies as Tools for Biofilm Characterization Created by Cariogenic Streptococci

Fourier transform infrared (FT-IR) and Raman spectroscopy and mapping were applied to the analysis of biofilms produced by bacteria of the genus Streptococcus. Bacterial biofilm, also called dental plaque, is the main cause of periodontal disease and tooth decay. It consists of a complex microbial community embedded in an extracellular matrix composed of highly hydrated extracellular polymeric substances and is a combination of salivary and bacterial proteins, lipids, polysaccharides, nucleic acids, and inorganic ions. This study confirms the value of Raman and FT-IR spectroscopies in biology, medicine, and pharmacy as effective tools for bacterial product characterization.

Planarity and out-of-plane vibrational modes of tryptophan and tyrosine in biomolecular modeling

Tryptophan and tyrosine are amino acids that play significant roles in the folding processes of proteins at water-membrane interfaces because of their amphipathic heteroaromatic rings. Employing appropriate heteroaromatic molecular structures is essential for obtaining accurate dynamics and predictive capabilities in molecular simulations of these amino acids. In this study, molecular dynamics simulations that applied the most recent version of the CHARMM36 force field were conducted on aqueous solutions of tryptophan and of tyrosine. Geometric analysis and dynamics quantified how aromatic rings deviated from planar structures and exhibited out-of-plane fluctuations. Radial distribution functions showed possible biological significance because the extent of ring planarity slightly affected local water concentrations near aromatic rings. Instantaneous all-atom normal mode analysis (NMA) and Fourier transformation of time autocorrelation functions of out-of-plane displacements were applied to study out-of-plane vibrations of atoms in these rings. The NMA started with minimum energy configurations and then averaged over fluctuations in aqueous solution. The frequencies and frequency patterns that were obtained for tryptophan and tyrosine with CHARMM36 differed from literature reports of Raman spectra, infrared spectra, and frequencies calculated using quantum mechanics, with some out-of-plane modes found at higher frequencies. Effects of imposing improper torsion potentials and changing torsion angle force constants were investigated for all atoms in the rings of tryptophan and tyrosine. Results show that these coarse force field variations only affect planarity and out-of-plane vibrations of atoms within the rings, and not other vibrations. Although increasing improper torsion force constants reduced deviations from aromatic ring planarity significantly, it increased out-of-plane mode frequencies. Reducing torsion angle force constants (with and without improper torsions) shifted modes to lower frequencies. A combination of decreasing most torsion angle force constants for ring atoms in both amino acids and including improper torsion forces attained frequencies and frequency patterns for out-of-plane normal modes that were more similar to the literature spectra. These force field variations decreased the extents of out-of-plane vibrations within the heteroaromatic rings of tryptophan, especially around the nitrogen atom in the ring, but not within the heteroaromatic ring of tyrosine. Conclusions were unaffected by the peptide endgroup, water, or simulation ensemble.

Disorder-to-Order Markers of a Cyclic Hexapeptide Inspired from the Binding Site of Fertilin β Involved in Fertilization Process

Synthetic peptides mimicking the binding site of fertilin β to its receptor, integrin α6β1, were shown to inhibit sperm-egg fusion when added to in vitro media. In contrast, the synthetic cyclic hexapeptide, cyclo(Cys¹-Ser²-Phe³-Glu⁴-Glu⁵-Cys⁶), named as cFEE, proved to stimulate gamete fusion. Owing to its biological specificity, this hexapeptide could help improve the in vitro fertilization pregnancy rate in human. In an attempt to establish the structure-activity relationship of cFEE, its structural dynamics was herein analyzed by means of ultraviolet circular dichroism (UV-CD) and Raman scattering. The low concentration CD profile in water, containing mainly a deep minimum at ∼202 nm, is consistent with a rather unordered chain. However, an ordering trend of the peptide loop has been observed in a less polar solvent such as methanol, where the UV-CD signal shape is formed by a double negative marker at ∼202/215 nm, indicating the presence of a type-II' β-turn. Raman spectra recorded in aqueous samples upon a 100-fold concentration increase, still showed an important population (∼30%) of the disordered structure. The structural flexibility of the disulfide bridge was confirmed by the Raman markers arising from the Cys¹-Cys⁶ disulfide bond-stretch motions. Density functional theory calculations highlighted the formation of the type-II' β-turn on the four central residues of cFEE (i.e., -Ser²-Phe³-Glu⁴-Glu⁵-) either with a left- or with a right-handed disulfide. The structure with a left-handed S-S bond, however, appears to be more stable.

Encapsulation of Aspartic Protease in Nonlamellar Lipid Liquid Crystalline Phases

Encapsulation of proteins within lipid inverse bicontinuous cubic phases (Q₂) has been widely studied for many applications, such as protein crystallization or drug delivery of proteins for food and pharmaceutical purposes. However, the use of the lipid sponge (L₃) phase for encapsulation of proteins has not yet been well explored. Here, we have employed a lipid system that forms highly swollen sponge phases to entrap aspartic protease (34 kDa), an enzyme used for food processing, e.g., to control the cheese-ripening process. Small-angle x-ray scattering showed that although the L₃ phase was maintained at low enzyme concentrations (≤15 mg/mL), higher concentration induces a transition to more curved structures, i.e., transition from L₃ to inverse bicontinuous cubic (Q₂) phase. The Raman spectroscopy data showed minor conformational changes assigned to the lipid molecules that confirm the lipid-protein interactions. However, the peaks assigned to the protein showed that the structure was not significantly affected. This was consistent with the higher activity presented by the encapsulated aspartic protease compared to the free enzyme stored at the same temperature. Finally, the encapsulation efficiency of aspartic protease in lipid sponge-like nanoparticles was 81% as examined by size-exclusion chromatography. Based on these results, we discuss the large potential of lipid sponge phases as carriers for proteins.

SERS Probing of Proteins in Gold Nanoparticle Agglomerates

The collection of surface-enhanced Raman scattering (SERS) spectra of proteins and other biomolecules in complex biological samples such as animal cells has been achieved with gold nanoparticles that are introduced to the sample. As a model for such a situation, SERS spectra were measured in protein solutions using gold nanoparticles in the absence of aggregating agents, allowing for the free formation of a protein corona. The SERS spectra indicate a varied interaction of the protein molecule with the gold nanoparticles, depending on protein concentration. The concentration-dependent optical properties of the formed agglomerates result in strong variation in SERS enhancement. At protein concentrations that correspond to those inside cells, SERS signals are found to be very low. The results suggest that in living cells the successful collection of SERS spectra must be due to the positioning of the aggregates rather than the crowded biomolecular environment inside the cells. Experiments with DNA suggest the suitability of the applied sample preparation approach for an improved understanding of SERS nanoprobes and nanoparticle-biomolecule interactions in general.

Raman tweezers microspectroscopy of circa 100 nm extracellular vesicles

The technique of Raman tweezers microspectroscopy (RTM) for the global biomolecular content characterization of a single extracellular vesicle (EV) or a small number of EVs or other nanoscale bioparticles in an aqueous dispersion in the difficult-to-access size range of near 100 nm is described in detail. The particularities and potential of RTM are demonstrated using the examples of DOPC liposomes, exosomes from human urine and rat hepatocytes, and a mixed sample of the transfection reagent FuGENE in diluted DNA solution. The approach of biomolecular component analysis for the estimation of the main biomolecular contributions (proteins, lipids, nucleic acids, carotenoids, etc.) is proposed and discussed. Direct Raman evidence for strong intra-sample biomolecular heterogeneity of individual optically trapped EVs, due to variable contributions from nucleic acids and carotenoids in some preparations, is reported. On the basis of the results obtained, we are making an attempt to convince the scientific community that RTM is a promising method of single-EV research; to our knowledge, it is the only technique available at the moment that provides unique information about the global biomolecular composition of a single vesicle or a small number of vesicles, thus being capable of unravelling the high diversity of EV subpopulations, which is one of the most significant urgent challenges to overcome. Possible RTM applications include, among others, searching for DNA biomarkers, cancer diagnosis, and discrimination between different subpopulations of EVs, lipid bodies, protein aggregates and viruses.

The control of the adsorption of bovine serum albumin on mercaptan-modified gold thin films investigated by SERS spectroscopy

Nanostructured gold thin films were built from deposition of colloidal gold nanoparticles on silanized glass slides, and used to study the adsorption of bovine serum albumin (BSA) after chemical treatment of gold surface with the mercaptans 2-mercaptoethanol, 3-mercaptoproprionic acid, 1,3-propanedithiol and 1-propanethiol. Surface-enhanced Raman scattering (SERS) spectroscopy was used for investigating the chemical interactions of BSA with the modified gold surfaces. In the presence of the surface modifier 2-mercaptoethanol, a promoter of hydrogen bonds, the stable interactions among BSA and gold surfaces led to high reproducibility of the SERS spectral pattern in the most monitored points of the mapped surface. The vibrational assignment endorsed the assumption that lysine residue, majority present in the molecular structure, were the principal anchor site of BSA involved in the interactions with 2-mercaptoethanol-modified gold surface.

Raman spectroscopy insight into Norovirus encapsulation in Bombyx mori cypovirus cubic microcrystals

Protein and amino acid structures of Norovirus-like particles (NoVLP) have been investigated by Raman spectroscopy before and after encapsulation into Bombyx mori cypovirus (BmCPV) cubic microcrystals, which are usually referred to as cubes or polyhedra. Two different types of tag were used in co-expression, namely VP3 and H1 tags. VP3 tag is derived from a capsid protein VP4 from BmCPV and H1 tag is N-terminal α-helix of BmCPV polyhedrin, respectively. A major capsid protein VP1 of NoVLP G11.4 was fused with H1 or VP3 tags, and then encapsulated into BmCPV polyhedra. Analyses of the spectroscopic data permitted the assignment of conformation-sensitive Raman bands to viral amino acid constituents and the observation of structural similarities or differences between differently tagged samples. Three separate Raman zones were attentioned, namely, the ring-mode structure region (1000-1500 cm^-1), the CO and CC double-bond region and its surroundings (1500-1750 cm^-1), and the high-frequency CH stretching region (2800-3100 cm^-1). Structural fingerprints could be found in specific spectral zones for differently co-expressed samples. One clear characteristic of the H1-tagged VP1 polyhedra was the increase in tyrosine fraction, which played a critical role in binding neighboring strands through its unpaired negatively charged COO^- sites. This feature could consistently be detected in different regions, but it was best represented by Raman signals associated with negatively charged COO^- sites and H1 helices in the double-bond region. Such peculiar chemical features were revealed by two relatively broad bands at 1570 and 1630 cm^-1, which were assigned to COO^- anti-symmetric stretching and amide I in 3₁₀-helix extensions to α-helices at N-termini, respectively. These specific features did not display in the spectrum of the VP3-tagged VP1 polyhedra. Concurrently, a strong reduction of CH bond Raman signal was noticed in the high frequency stretching region of the Raman spectrum upon H1-tagged VP1 polyhedra. The Raman activity most strikingly also represented fingerprints of tagged NoVLP VP1 after its encapsulation into BmCPV polyhedra, opening thus the possibility to in situ advanced experiments in the fields of drug delivery and regenerative medicine.

Dynamical Behavior of Somatostatin-14 and Its Cyclic Analogues as Analyzed in Bulk and on Plasmonic Silver Nanoparticles

Primarily known as the inhibitor of growth hormone release, the role of somatostatin in many other inhibiting activities upon binding to its five G-protein-coupled receptors has been elucidated. Because of the short half-life of somatostatin, a number of synthetic analogues were elaborated for this peptide hormone. Herein, after recalling the main somatostatin therapeutic interests, we present the dynamical behavior of somatostatin-14 and its two currently used synthetic cyclic analogues, octreotide and pasireotide. Physical techniques, such as fluorescence, UV-visible absorption, circular dichroism, Raman spectroscopy, surface-enhanced Raman spectroscopy, and transmission electron microscopy, were jointly used in order to get information on the solution structural features, as well as on the anchoring sites of the three peptides on silver colloids. While somatostatin-14 adopts a rather unordered chain within the submillimolar concentration range, its cyclic analogues were revealed to be ordered, i.e., stabilized either in a type-II' β-turn (octreotide) or in a face-to-face γ-turn/type-I β-turn (pasireotide) structure. Nevertheless, a progressive structuring trend was observed in somatostatin-14 upon increasing concentration to the millimolar range. Because of their cationic character, the three peptides have revealed their capability to bind onto negatively charged silver nanoparticles. The high affinity of the peptides toward metallic particles seems to be extremely promising for the elaboration of somatostatin-based functionalized plasmonic nanoparticles that can be used in diagnosis, drug delivery, and therapy.

Insights of adsorption mechanisms of Trp-peptides on plasmonic surfaces by SERS

The adsorptions of tryptophan (Trp) on silver or gold surfaces were investigated by surface-enhanced Raman scattering (SERS) measurements. In addition, peptides with Trp in different chain positions were studied and the adsorption sites were determined based on marker bands. The indole ring was the main group responsible for the interactions with gold nanoparticles (AuNPs). In the presence of HCl, the SERS spectra suggested that the anchoring of such peptides on AuNPs was reinforced by ionic pair interactions between protonated amine and chloride ions. The adsorptions of Trp and its derivatives on silver nanoparticles (AgNPs) show some variability in the spectral patterns, even though the enhanced carboxilate and amino features were ever ascribed as preferable adsorption site. Based on DFT calculations the vibrational assignment allows the reinterpretation of previous published works. The investigations showed that both the high affinity of indole moiety for the AuNP surfaces make these substrates adequate for studying the adsorption of peptides containing Trp and the proposed SERS assignments could be helpful for further studies of more complex structures.

Efficient structural elucidation of microhydrated biomolecules through the interrogation of hydrogen bond networks

Pattern analysis of H-bond networks through a graph-theoretic method is very effective in determining the global minima of microhydrated biomolecules.

Drop coating deposition Raman spectroscopy of proteinogenic amino acids compared with their solution and crystalline state

The Raman spectra of 20 proteinogenic amino acids were recorded in the solution, glass phase (as drop coating deposition Raman (DCDR) samples) and crystalline forms in the wide spectral range of 200-3200cm^-1. The most apparent spectral differences between the Raman spectra of the crystalline forms, glass phases and aqueous solutions of amino acids were briefly discussed and described in the frame of published works. The possible density dependencies of spectral bands were noted. In some cases, a strong influence of the sample density, as well as of the organization of the water envelope, was observed. The most apparent changes were observed for Ser and Thr. Nevertheless, for the majority of amino acids, the DCDR sample form is an intermediate between the solution and crystalline forms. In contrast, aromatic amino acids have only a small sensitivity to the form of the sample. Our reference set of Raman spectra is useful for revealing discrepancies between the SERS and solid/solution spectra of amino acids. We also found that some previously published Raman spectra of polycrystalline samples resemble glassy state rather than crystalline spectra. Therefore, this reference set of spectra will find application in every branch of Raman spectroscopy where the spectra of biomolecules are collected from coatings.

[Impairments of placental amino acid metabolism in fetal growth restriction]

The content of the amino acids in the placenta during physiological pregnancy and fetal growth restriction (FGR) has been investigated my means of the method of ion-exchange chromatography. It has been found that in FGR the placental amino acid pool is characterized by a decreased content of arginine, proline, alanine, serine, cysteine, methionine, tryptophan, leucine, threonine, tyrosine, phenylalanine, glutamine and an increased content of dicarboxylic amino acids, lysine, histidine and glycine. These changes are accompanied by altered activity of some enzymes of amino acid metabolism, and the degree of these changes correlates with the level of corresponding amino acids.

Physicochemical properties and in vitro cytotoxicity of iron oxide-based nanoparticles modified with antiangiogenic and antitumor peptide A7R

Superparamagnetic iron oxide-based nanoparticles (SPIONs) are promising carriers as targeted drug delivery vehicles, because they can be guided to their target with the help of an external magnetic field. Functionalization of nanoparticles' surface with molecules, which bind with high affinity to receptors on target tissue significantly facilitates delivery of coated nanoparticles to their targeted site. Here, we demonstrate conjugation of an antiangiogenic and antitumor peptide ATWLPPR (A7R) to SPIONs modified with sebacic acid (SPIONs-SA). Successful conjugation was confirmed by various analytical techniques (FTIR, SERS, SEM-EDS, TEM, TGA). Cell cytotoxicity studies, against two cell lines (HUVEC and MDA-MB-231) indicated that SPIONs modified with A7R reduced HUVEC cell viability at concentrations higher than 0.01 mg Fe/mL, in comparison to cells that were exposed to either the nanoparticles modified with sebacic acid or A7R peptide solely, what might be partially caused by a process of internalization.

Privileged hydration sites in aromatic side chains: effect on conformational equilibrium

The most energetically favourable hydration sites of aromatic (Phe, Tyr, Trp and His) side chains revealed by DFT-based theoretical calculations.