RESUMO
The widespread ability of proteins and peptides to self-assemble by forming cross-ß structure is one of the most significant discoveries in structural biology. Intriguingly, the cross-ß association of proteins/peptides may generate intricate supramolecular architectures with uncommon spectroscopic properties. We have recently characterized self-assembled peptides extracted from the PREP1 protein that are endowed with interesting structural/spectroscopic properties. We here demonstrate that the green fluorescence emission of the peptide PREP1[117-132] (λem ~520â nm), can be induced by excitation with UV radiation. The associated unusually large Stokes shift (Δλ ~150â nm) represents, to the best of our knowledge, the first evidence of an internal resonance energy transfer in amyloid-like structures, where the blue emission of some assemblies becomes the excitation radiation for others. Moreover, the characterization of PREP1[117-132] variants provides insights into the sequence/structure and structure/spectroscopic properties relationships. Our data suggests that the green fluorescence is plausibly associated with antiparallel ß-sheet states of the peptide whereas parallel ß-sheet assemblies are only endowed with blue fluorescence. Notably, the different PREP1[117-132] variants also form assemblies characterized by distinct morphologies. Indeed, the parent peptide and single mutants form compact but structured aggregates whereas most of the double mutants exhibit elongated and highly extended fibers.
Assuntos
Amiloide , Peptídeos , Peptídeos/química , Amiloide/química , Espectrometria de Fluorescência , Sequência de AminoácidosRESUMO
Peptides are able to self-organize in structural elements including cross-ß structures. Taking advantage of this tendency, in the last decades, peptides have been scrutinized as molecular elements for the development of multivalent supramolecular architectures. In this context, different classes of peptides, also with completely aromatic sequences, were proposed. Our previous studies highlighted that the (FY)3 peptide, which alternates hydrophobic phenylalanine and more hydrophilic tyrosine residues, is able to self-assemble, thanks to the formation of both polar and apolar interfaces. It was observed that the replacement of Phe and Tyr residues with other noncoded aromatic amino acids like 2-naphthylalanine (Nal) and Dopa affects the interactions among peptides with consequences on the supramolecular organization. Herein, we have investigated the self-assembling behavior of two novel (FY)3 analogues with Trp and Dopa residues in place of the Phe and Tyr ones, respectively. Additionally, PEGylation of the N-terminus was analyzed too. The supramolecular organization, morphology, and capability to gel were evaluated using complementary techniques, including fluorescence, Fourier transform infrared spectroscopy, and scanning electron microscopy. Structural periodicities along and perpendicular to the fiber axis were detected by grazing incidence wide-angle X-ray scattering. Finally, molecular dynamics studies provided interesting insights into the atomic structure of the cross-ß that constitutes the basic motif of the assemblies formed by these novel peptide systems.
Assuntos
Triptofano , Tirosina , Tirosina/química , Triptofano/química , Di-Hidroxifenilalanina , Peptídeos/química , Aminoácidos Aromáticos/químicaRESUMO
KCTD ((K)potassium Channel Tetramerization Domain-containing) proteins constitute an emerging class of proteins involved in fundamental physio-pathological processes. In these proteins, the BTB domain, which represents the defining element of the family, may have the dual role of promoting oligomerization and favoring functionally important partnerships with different interactors. Here, by exploiting the potential of recently developed methodologies for protein structure prediction, we report a comprehensive analysis of the interactions of all KCTD proteins with their most common partner Cullin 3 (Cul3). The data here presented demonstrate the impressive ability of this approach to discriminate between KCTDs that interact with Cul3 and those that do not. Indeed, reliable and stable models of the complexes were only obtained for the 15 members of the family that are known to interact with Cul3. The generation of three-dimensional models for all KCTD-Cul3 complexes provides interesting clues on the determinants of the structural basis of this partnership as clear structural differences emerged between KCTDs that bind or do not bind Cul3. Finally, the availability of accurate three-dimensional models for KCTD-Cul3 interactions may be valuable for the ad hoc design and development of compounds targeting specific KCTDs that are involved in several common diseases.
Assuntos
Proteínas Culina , Canais de Potássio , Humanos , Sequência de Aminoácidos , Proteínas Culina/química , Canais de Potássio/química , Ligação Proteica , Multimerização ProteicaRESUMO
A detailed comprehension of MHC-epitope recognition is essential for the design and development of new antigens that could be effectively used in immunotherapy. Yet, the high variability of the peptide together with the large abundance of MHC variants binding makes the process highly specific and large-scale characterizations extremely challenging by standard experimental techniques. Taking advantage of the striking predictive accuracy of AlphaFold, we report a structural and dynamic-based strategy to gain insights into the molecular basis that drives the recognition and interaction of MHC class I in the immune response triggered by pathogens and/or tumor-derived peptides. Here, we investigated at the atomic level the recognition of E7 and TRP-2 epitopes to their known receptors, thus offering a structural explanation for the different binding preferences of the studied receptors for specific residues in certain positions of the antigen sequences. Moreover, our analysis provides clues on the determinants that dictate the affinity of the same epitope with different receptors. Collectively, the data here presented indicate the reliability of the approach that can be straightforwardly extended to a large number of related systems.
Assuntos
Peptídeos , Epitopos , Reprodutibilidade dos Testes , Peptídeos/químicaRESUMO
Aptamers are synthetic nucleic acids that are developed to target with high affinity and specificity chemical entities ranging from single ions to macromolecules and present a wide range of chemical and physical properties. Their ability to selectively bind proteins has made these compounds very attractive and versatile tools, in both basic and applied sciences, to such an extent that they are considered an appealing alternative to antibodies. Here, by exhaustively surveying the content of the Protein Data Bank (PDB), we review the structural aspects of the protein-aptamer recognition process. As a result of three decades of structural studies, we identified 144 PDB entries containing atomic-level information on protein-aptamer complexes. Interestingly, we found a remarkable increase in the number of determined structures in the last two years as a consequence of the effective application of the cryo-electron microscopy technique to these systems. In the present paper, particular attention is devoted to the articulated architectures that protein-aptamer complexes may exhibit. Moreover, the molecular mechanism of the binding process was analyzed by collecting all available information on the structural transitions that aptamers undergo, from their protein-unbound to the protein-bound state. The contribution of computational approaches in this area is also highlighted.
Assuntos
Aptâmeros de Nucleotídeos , Ácidos Nucleicos , Microscopia Crioeletrônica , Aptâmeros de Nucleotídeos/química , Proteínas/química , AnticorposRESUMO
Protein-protein interfaces play fundamental roles in the molecular mechanisms underlying pathophysiological pathways and are important targets for the design of compounds of therapeutic interest. However, the identification of binding sites on protein surfaces and the development of modulators of protein-protein interactions still represent a major challenge due to their highly dynamic and extensive interfacial areas. Over the years, multiple strategies including structural, computational, and combinatorial approaches have been developed to characterize PPI and to date, several successful examples of small molecules, antibodies, peptides, and aptamers able to modulate these interfaces have been determined. Notably, peptides are a particularly useful tool for inhibiting PPIs due to their exquisite potency, specificity, and selectivity. Here, after an overview of PPIs and of the commonly used approaches to identify and characterize them, we describe and evaluate the impact of chemical peptide libraries in medicinal chemistry with a special focus on the results achieved through recent applications of this methodology. Finally, we also discuss the role that this methodology can have in the framework of the opportunities, and challenges that the application of new predictive approaches based on artificial intelligence is generating in structural biology.
Assuntos
Inteligência Artificial , Biblioteca de Peptídeos , Peptídeos/química , Sítios de Ligação , Proteínas de Membrana , Ligação ProteicaRESUMO
Amyloid aggregation is a widespread process that involves proteins and peptides with different molecular complexity and amino acid composition. The structural motif (cross-ß) underlying this supramolecular organization generates aggregates endowed with special mechanical and spectroscopic properties with huge implications in biomedical and technological fields, including emerging precision medicine. The puzzling ability of these assemblies to emit intrinsic and label-free fluorescence in regions of the electromagnetic spectrum, such as visible and even infrared, usually considered to be forbidden in the polypeptide chain, has attracted interest for its many implications in both basic and applied science. Despite the interest in this phenomenon, the physical basis of its origin is still poorly understood. To gain a global view of the available information on this phenomenon, we here provide an exhaustive survey of the current literature in which original data on this fluorescence have been reported. The emitting systems have been classified in terms of their molecular complexity, amino acid composition, and physical state. Information about the wavelength of the radiation used for the excitation as well as the emission range/peak has also been retrieved. The data collected here provide a picture of the complexity of this multifaceted phenomenon that could be helpful for future studies aimed at defining its structural and electronic basis and/or stimulating new applications.
Assuntos
Amiloide , Peptídeos , Fluorescência , Peptídeos/química , Amiloide/química , Proteínas Amiloidogênicas , AminoácidosRESUMO
Tetrameric hemoglobins (Hbs) are prototypal systems for studies aimed at unveiling basic structure-function relationships as well as investigating the molecular/structural basis of adaptation of living organisms to extreme conditions. However, a chronological analysis of decade-long studies conducted on Hbs is illuminating on the difficulties associated with the attempts of gaining functional insights from static structures. Here, we applied molecular dynamics (MD) simulations to explore the functional transition from the T to the R state of the hemoglobin of the Antarctic fish Trematomus bernacchii (HbTb). Our study clearly demonstrates the ability of the MD technique to accurately describe the transition of HbTb from the T to R-like states, as shown by a number of global and local structural indicators. A comparative analysis of the structural states that HbTb assumes in the simulations with those detected in previous MD analyses conducted on HbA (human Hb) highlights interesting analogies (similarity of the transition pathway) and differences (distinct population of intermediate states). In particular, the ability of HbTb to significantly populate intermediate states along the functional pathway explains the observed propensity of this protein to assume these structures in the crystalline state. It also explains some functional data reported on the protein that indicate the occurrence of other functional states in addition to the canonical R and T ones. These findings are in line with the emerging idea that the classical two-state view underlying tetrameric Hb functionality is probably an oversimplification and that other structural states play important roles in these proteins. The ability of MD simulations to accurately describe the functional pathway in tetrameric Hbs suggests that this approach may be effectively applied to unravel the molecular and structural basis of Hbs exhibiting peculiar functional properties as a consequence of the environmental adaptation of the host organism.
Assuntos
Hemoglobinas , Perciformes , Animais , Regiões Antárticas , Hemoglobinas/química , Hemoglobinas/metabolismo , Humanos , Simulação de Dinâmica Molecular , Oxigênio/química , Perciformes/metabolismoRESUMO
Oligomerization endows proteins with some key properties such as extra-stabilization, long-range allosteric regulation(s), and partnerships not accessible to their monomeric counterparts. How oligomerization is achieved and preserved during evolution is a subject of remarkable scientific relevance. By exploiting the abilities of the machine-learning algorithms implemented in AlphaFold (AF) in predicting protein structures, herein, we report a comprehensive analysis of the structural states of functional oligomers of all members of the KCTD protein family. Interestingly, our approach led to the identification of reliable three-dimensional models for the pentameric states of KCNRG, KCTD6, KCTD4, KCTD7, KCTD9, and KCTD14 and possibly for KCTD11 and KCTD21 that are involved in key biological processes and that were previously uncharacterized from a structural point of view. Although for most of these proteins, the CTD domains lack any sequence similarity, they share some important structural features, such as a propeller-like structure with a central cavity delimited by five exposed and regular ß-strands. Moreover, the structure of the related proteins KCTD7 and KCTD14, although pentameric, appears to be characterized by a different organization of the CTD region, with the five chains forming a circle-like structure with a large cavity. Our predictions also suggest that other members of the family, such as KCTD10, KCTD13, and TNFAIP1, present a strong propensity to assume dimeric states. Although the structures of the functional oligomers reported herein represent models that require additional validations, they provide a consistent and global view of KCTD protein oligomerization.
Assuntos
Canais de Potássio , Proteínas , Ligação Proteica , Canais de Potássio/metabolismo , Proteínas/metabolismoRESUMO
The antigenicity as well as the immunogenicity of tumor associated antigens (TAAs) may need to be potentiated in order to break the immunological tolerance. To this aim, heteroclitic peptides were designed introducing specific substitutions in the residue at position 4 (p4) binding to TCR. The effect of such modifications also on the affinity to the major histocompatibility class I (MHC-I) molecule was assessed. The Trp2 antigen, specific for the mouse melanoma B16F10 cells, as well as the HPV-E7 antigen, specific for the TC1 tumor cell lines, were used as models. Affinity of such heteroclitic peptides to HLA was predicted by bioinformatics tools and the most promising ones were validated by structural conformational and HLA binding analyses. Overall, we demonstrated that TAAs modified at the TCR-binding p4 residue are predicted to have higher affinity to MHC-I molecules. Experimental evaluation confirms the stronger binding, suggesting that this strategy may be very effective for designing new vaccines with improved antigenic efficacy.
Assuntos
Antígeno HLA-A2 , Peptídeos , Animais , Antígenos de Neoplasias , Camundongos , Ligação Proteica , Receptores de Antígenos de Linfócitos TRESUMO
Peptide-based hydrogels, originated by multiscale self-assembling phenomenon, have been proposed as multivalent tools in different technological areas. Structural studies and molecular dynamics simulations pointed out the capability of completely aromatic peptides to gelificate if hydrophilic and hydrophobic forces are opportunely balanced. Here, the effect produced by the introduction of a Cys residue in the heteroaromatic sequence of (FY)3 and in its PEGylated variant was evaluated. The physicochemical characterization indicates that both FYFCFYF and PEG8-FYFCFYF are able to self-assemble in supramolecular nanostructures whose basic cross-ß motif resembles the one detected in the ancestor (FY)3 assemblies. However, gelification occurs only for FYFCFYF at a concentration of 1.5â wt%. After cross-linking of cysteine residues, the hydrogel undergoes to an improvement of the rigidity compared to the parent (FY)3 assemblies as suggested by the storage modulus (G') that increases from 970 to 3360â Pa. The mechanical properties of FYFCFYF are compatible with its potential application in bone tissue regeneration. Moreover, the avalaibility of a Cys residue in the middle of the peptide sequence could allow the hydrogel derivatization with targeting moieties or with biologically relevant molecules.
Assuntos
Cisteína , Hidrogéis , Sequência de Aminoácidos , Simulação de Dinâmica Molecular , PeptídeosRESUMO
Analysis of the intrinsic UV-visible fluorescence exhibited by self-assembling amyloid-like peptides in solution and in solid the state highlights that their physical state has a profound impact on the optical properties. In the solid state, a linear dependence of the fluorescence emission peaks as a function of excitation wavelength is detected. On the contrary, an excitation-independent emission is observed in solution. The present findings constitute a valuable benchmark for current and future explanations of the fluorescence emission by amyloids.
Assuntos
Amiloide/química , Fluorescência , Peptídeos/química , Soluções , Raios UltravioletaRESUMO
Human hemoglobin (HbA) is one of the prototypal systems used to investigate structure-function relationships in proteins. Indeed, HbA has been used to develop the basic concepts of protein allostery, although the atomic-level mechanism underlying the HbA functionality is still highly debated. This is due to the fact that most of the three-dimensional structural information collected over the decades refers to the endpoints of HbA functional transition with little data available for the intermediate states. Here, we report molecular dynamics (MD) simulations by focusing on the relevance of the intermediate states of the protein functional transition unraveled by the crystallographic studies carried out on vertebrate Hbs. Fully atomistic simulations of the HbA T-state indicate that the protein undergoes a spontaneous transition toward the R-state. The inspection of the trajectory structures indicates that the protein significantly populates the intermediate HL-(C) state previously unraveled by crystallography. In the structural transition, it also assumes the intermediate states crystallographically detected in Antarctic fish Hbs. This finding suggests that HbA and Antarctic fish Hbs, in addition to the endpoints of the transitions, also share a similar deoxygenation pathway despite a distace of hundreds of millions of years in the evolution scale. Finally, using the essential dynamic sampling methodology, we gained some insights into the reverse R to T transition that is not spontaneously observed in classic MD simulations.
Assuntos
Hemoglobinas , Simulação de Dinâmica Molecular , Animais , Cristalografia , Humanos , Estrutura Quaternária de ProteínaRESUMO
Thrombin is the key enzyme of the entire hemostatic process since it is able to exert both procoagulant and anticoagulant functions; therefore, it represents an attractive target for the developments of biomolecules with therapeutic potential. Thrombin can perform its many functional activities because of its ability to recognize a wide variety of substrates, inhibitors, and cofactors. These molecules frequently are bound to positively charged regions on the surface of protein called exosites. In this review, we carried out extensive analyses of the structural determinants of thrombin partnerships by surveying literature data as well as the structural content of the Protein Data Bank (PDB). In particular, we used the information collected on functional, natural, and synthetic molecular ligands to define the anatomy of the exosites and to quantify the interface area between thrombin and exosite ligands. In this framework, we reviewed in detail the specificity of thrombin binding to aptamers, a class of compounds with intriguing pharmaceutical properties. Although these compounds anchor to protein using conservative patterns on its surface, the present analysis highlights some interesting peculiarities. Moreover, the impact of thrombin binding aptamers in the elucidation of the cross-talk between the two distant exosites is illustrated. Collectively, the data and the work here reviewed may provide insights into the design of novel thrombin inhibitors.
Assuntos
Aptâmeros de Nucleotídeos/metabolismo , Hemostáticos/metabolismo , Trombina/metabolismo , Animais , Aptâmeros de Nucleotídeos/química , Sítios de Ligação , Hemostáticos/química , Humanos , Ligantes , Modelos Moleculares , Ligação Proteica , Especificidade por Substrato , Trombina/químicaRESUMO
The three members (GADD45α, GADD45ß, and GADD45γ) of the growth arrest and DNA damage-inducible 45 (GADD45) protein family are involved in a myriad of diversified cellular functions. With the aim of unravelling analogies and differences, we performed comparative biochemical and biophysical analyses on the three proteins. The characterization and quantification of their binding to the MKK7 kinase, a validated functional partner of GADD45ß, indicate that GADD45α and GADD45γ are strong interactors of the kinase. Despite their remarkable sequence similarity, the three proteins present rather distinct biophysical properties. Indeed, while GADD45ß and GADD45γ are marginally stable at physiological temperatures, GADD45α presents the Tm value expected for a protein isolated from a mesophilic organism. Surprisingly, GADD45α and GADD45ß, when heated, form high-molecular weight species that exhibit features (ThT binding and intrinsic label-free UV/visible fluorescence) proper of amyloid-like aggregates. Cell viability studies demonstrate that they are endowed with a remarkable toxicity against SHSY-5Y and HepG2 cells. The very uncommon property of GADD45ß to form cytotoxic species in near-physiological conditions represents a puzzling finding with potential functional implications. Finally, the low stability and/or the propensity to form toxic species of GADD45 proteins constitute important features that should be considered in interpreting their many functions.
Assuntos
Amiloide/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/química , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Agregados Proteicos , Amiloide/química , Sobrevivência Celular , Células Cultivadas , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/genética , MAP Quinase Quinase 7/metabolismo , Agregação Patológica de Proteínas/metabolismo , Ligação Proteica , Conformação Proteica em Folha beta , Estabilidade Proteica , Proteínas Recombinantes , Termodinâmica , Proteínas GADD45RESUMO
The arginine binding protein from T. maritima (ArgBP) exhibits several distinctive biophysical and structural properties. Here we show that ArgBP is also endowed with a ramarkable pressure stability as it undergoes minor structural changes only, even at 10 kbar. A similar stability is also observed for its folded fragments (truncated monomer and individual domains). A survey of literature data on the pressure stability of proteins highlights the uncommon behavior of ArgBP.
Assuntos
Proteínas de Bactérias/química , Proteínas de Transporte/química , Thermotoga maritima/química , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Proteínas de Transporte/genética , Pressão , Conformação Proteica , Domínios Proteicos , Estabilidade Proteica , Deleção de Sequência , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
Arginine is one of the most important nutrients of living organisms as it plays a major role in important biological pathways. However, the accumulation of arginine as consequence of metabolic defects causes hyperargininemia, an autosomal recessive disorder. Therefore, the efficient detection of the arginine is a field of relevant biomedical/biotechnological interest. Here, we developed protein variants suitable for arginine sensing by mutating and dissecting the multimeric and multidomain structure of Thermotoga maritima arginine-binding protein (TmArgBP). Indeed, previous studies have shown that TmArgBP domain-swapped structure can be manipulated to generate simplified monomeric and single domain scaffolds. On both these stable scaffolds, to measure tryptophan fluorescence variations associated with the arginine binding, a Phe residue of the ligand binding pocket was mutated to Trp. Upon arginine binding, both mutants displayed a clear variation of the Trp fluorescence. Notably, the single domain scaffold variant exhibited a good affinity (~3 µM) for the ligand. Moreover, the arginine binding to this variant could be easily reverted under very mild conditions. Atomic-level data on the recognition process between the scaffold and the arginine were obtained through the determination of the crystal structure of the adduct. Collectively, present data indicate that TmArgBP scaffolds represent promising candidates for developing arginine biosensors.
Assuntos
Arginina/química , Arginina/metabolismo , Fenômenos Fisiológicos Bacterianos , Proteínas de Transporte/química , Proteínas de Transporte/metabolismo , Thermotoga maritima/metabolismo , Proteínas de Transporte/genética , Hiperargininemia/diagnóstico , Hiperargininemia/etiologia , Hiperargininemia/metabolismo , Ligantes , Modelos Moleculares , Mutação , Ligação Proteica , Conformação Proteica , Domínios e Motivos de Interação entre Proteínas , Relação Estrutura-Atividade , Thermotoga maritima/genéticaRESUMO
Studies carried out in recent decades have revealed that the ability to self-assemble is a widespread property among biomolecules. Small nucleic acid moieties or very short peptides are able to generate intricate assemblies endowed with remarkable structural and spectroscopic properties. Herein, the structural/spectroscopic characterization of aggregates formed by nucleobases and peptide nucleic acid (PNA)-peptide conjugates are reported. At high concentration, all studied nucleobases form aggregates characterized by previously unreported fluorescence properties. The conjugation of these bases, as PNA derivatives, to the dipeptide Phe-Phe leads to the formation of novel hybrid assemblies, which are characterized by an amyloid-like association of the monomers. Although these compounds share the same basic cross-ß motif, the nature and number of PNA units have an important impact on both the level of structural order and the intrinsic fluorescence of the self-assembled nanostructure.
Assuntos
Ácidos Nucleicos Peptídicos/química , Fenilalanina/análogos & derivados , Dipeptídeos , Microscopia de Fluorescência , Nanoestruturas/química , Fenilalanina/química , Difração de Raios XRESUMO
Thermotoga maritima Arginine Binding Protein (TmArgBP) is a valuable candidate for arginine biosensing in diagnostics. This protein is endowed with unusual structural properties that include an extraordinary thermal/chemical stability, a domain swapped structure that undergoes large tertiary and quaternary structural transition, and the ability to form non-canonical oligomeric species. As the intrinsic stability of TmArgBP allows for extensive protein manipulations, we here dissected its structure in two parts: its main body deprived of the swapping fragment (TmArgBP20-233) and the C-terminal peptide corresponding to the helical swapping element. Both elements have been characterized independently or in combination using a repertoire of biophysical/structural techniques. Present investigations clearly indicate that TmArgBP20-233 represents a better scaffold for arginine sensing compared to the wild-type protein. Moreover, our data demonstrate that the ligand-free and the ligand-bound forms respond very differently to this helix deletion. This drastic perturbation has an important impact on the ligand-bound form of TmArgBP20-233 stability whereas it barely affects its ligand-free state. The crystallographic structures of these forms provide a rationale to this puzzling observation. Indeed, the arginine-bound state is very rigid and virtually unchanged upon protein truncation. On the other hand, the flexible ligand-free TmArgBP20-233 is able to adopt a novel state as a consequence of the helix deletion. Therefore, the flexibility of the ligand-free form endows this state with a remarkable robustness upon severe perturbations. In this scenario, TmArgBP dissection highlights an intriguing connection between destabilizing/stabilizing effects and the overall flexibility that could operate also in other proteins.
Assuntos
Arginina/química , Proteínas de Bactérias/química , Thermotoga maritima/metabolismo , Sequência de Aminoácidos , Proteínas de Bactérias/metabolismo , Proteínas de Bactérias/fisiologia , Técnicas Biossensoriais , Clonagem Molecular , Ligantes , Modelos Moleculares , Ligação Proteica , Domínios ProteicosRESUMO
Phenylalanine-based nanostructures have attracted the attention of the material science community for their functional properties. These properties strongly depend on the hierarchic organization of the nanostructure that in turn can be finely tuned by punctual chemical modifications of the building blocks. Herein, we investigate how the partial or the complete replacement of the Phe residues in PEG8 -(Phe)6 (PEG8 -F6) with tyrosines to generate PEG8 -(Phe-Tyr)3 (PEG8 -(FY)3) or PEG8 -(Tyr)6 (PEG8 -Y6) affects the structural/functional properties of the nanomaterial formed by the parental compound. Moreover, the effect of the PEG derivatization was evaluated through the characterization of the peptides without the PEG moiety (Tyr)6 (Y6) and (Phe-Tyr)3 ((FY)3). Both PEG8 -Y6 and PEG8 -(FY)3 can self-assemble in water at micromolar concentrations in ß-sheet-rich nanostructures. However, WAXS diffraction patterns of these compounds present significant differences. PEG8 -(FY)3 shows a 2D WAXS oriented fiber diffraction profile characterized by the concomitant presence of a 4.7â Å meridional and a 12.5â Å equatorial reflection that are generally associated with cross-ß structure. On the other hand, the pattern of PEG8 -Y6 is characterized by the presence of circles typically observed in the presence of PEG crystallization. Molecular modeling and dynamics provide an atomic structural model of the peptide spine of these compounds that is in good agreement with WAXS experimental data. Gelation phenomenon was only detected for PEG8 -(FY)3 above a concentration of 1.0â wt % as confirmed by storage (G'≈100â Pa) and loss (G''≈28â Pa) moduli in rheological studies. The cell viability on CHO cells of this soft hydrogel was certified to be 90 % after 24â hours of incubation.