Delia Picone

Professor of General and Inorganic Chemistry

Name Delia
Surname Picone
Institution University of Naples – Federico II
Address Department of Chemical Sciences, University of Naples Federico II, Complesso Universitario di Monte Sant'Angelo, Via Cintia, I-80126 Napoli, Italy
Delia Picone


  • Structural effects of methylglyoxal glycation, a study on the model protein MNEI.

    Publication Date: 16/07/2018 on Molecular and cellular biochemistry
    by Leone S, Fonderico J, Melchiorre C, Carpentieri A, Picone D
    DOI: 10.1007/s11010-018-3403-z

    The reaction of free amino groups in proteins with reactive carbonyl species, known as glycation, leads to the formation of mixtures of products, collectively referred to as advanced glycation endproducts (AGEs). These compounds have been implicated in several important diseases, but their role in pathogenesis and clinical symptoms' development is still debated. Particularly, AGEs are often associated to the formation of amyloid deposits in conformational diseases, such as Alzheimer's and Parkinson's disease, and it has been suggested that they might influence the mechanisms and kinetics of protein aggregation. We here present the characterization of the products of glycation of the model protein MNEI with methylglyoxal and their effect on the protein structure. We demonstrate that, despite being an uncontrolled process, glycation occurs only at specific residues of the protein. Moreover, while not affecting the protein fold, it alters its shape and hydrodynamic properties and increases its tendency to fibrillar aggregation. Our study opens the way to in deep structural investigations to shed light on the complex link between protein post-translational modifications, structure, and stability.

  • Glycation affects fibril formation of Aβ peptides.

    Publication Date: 29/06/2018 on The Journal of biological chemistry
    by Emendato A, Milordini G, Zacco E, Sicorello A, Dal Piaz F, Guerrini R, Thorogate R, Picone D, Pastore A
    DOI: 10.1074/jbc.RA118.002275

    Increasing evidence shows that Aβ peptides, which are associated with Alzheimer disease (AD), are heavily glycated in patients, suggesting a role of this irreversible non-enzymatic post-translational modification in pathology. Previous reports have shown that glycation increases the toxicity of the Aβ peptides although little is known about the mechanism. Here, we used the natural metabolic byproduct methylglyoxal as a glycating agent and exploited various spectroscopic methods and atomic force microscopy to study how glycation affects the structures of the Aβ40 and Aβ42 peptides, the aggregation pathway, and the morphologies of the resulting aggregates. We found that glycation significantly slows down but does not prevent β-conversion to mature fibres. We propose that the previously reported higher toxicity of the glycated Aβ peptides could be explained by a longer persistence in an oligomeric form, usually believed to be the toxic species.

  • High-level production of single chain monellin mutants with enhanced sweetness and stability in tobacco chloroplasts.

    Publication Date: 18/05/2018 on Planta
    by Castiglia D, Leone S, Tamburino R, Sannino L, Fonderico J, Melchiorre C, Carpentieri A, Grillo S, Picone D, Scotti N
    DOI: 10.1007/s00425-018-2920-z

    Plastid-based MNEI protein mutants retain the structure, stability and sweetness of their bacterial counterparts, confirming the attractiveness of the plastid transformation technology for high-yield production of recombinant proteins. The prevalence of obesity and diabetes has dramatically increased the industrial demand for the development and use of alternatives to sugar and traditional sweeteners. Sweet proteins, such as MNEI, a single chain derivative of monellin, are the most promising candidates for industrial applications. In this work, we describe the use of tobacco chloroplasts as a stable plant expression platform to produce three MNEI protein mutants with improved taste profile and stability. All plant-based proteins were correctly expressed in tobacco chloroplasts, purified and subjected to in-depth chemical and sensory analyses. Recombinant MNEI mutants showed a protein yield ranging from 5% to more than 50% of total soluble proteins, which, to date, represents the highest accumulation level of MNEI mutants in plants. Comparative analyses demonstrated the high similarity, in terms of structure, stability and function, of the proteins produced in plant chloroplasts and bacteria. The high yield and the extreme sweetness perceived for the plant-derived proteins prove that plastid transformation technology is a safe, stable and cost-effective production platform for low-calorie sweeteners, with an estimated production of up to 25-30 mg of pure protein/plant.

  • pH driven fibrillar aggregation of the super-sweet protein Y65R-MNEI: A step-by-step structural analysis.

    Publication Date: 27/12/2017 on Biochimica et biophysica acta
    by Pica A, Leone S, Di Girolamo R, Donnarumma F, Emendato A, Rega MF, Merlino A, Picone D
    DOI: 10.1016/j.bbagen.2017.12.012

    MNEI and its variant Y65R-MNEI are sweet proteins with potential applications as sweeteners in food industry. Also, they are often used as model systems for folding and aggregation studies.

  • Onconase Dimerization Through 3D Domain Swapping: Structural Investigations and Increase Of The Apoptotic Effect In Cancer Cells.

    Publication Date: 28/09/2017 on The Biochemical journal
    by Fagagnini A, Pica A, Fasoli S, Montioli R, Donadelli M, Cordani M, Butturini E, Acquasaliente L, Picone D, Gotte G
    DOI: 10.1042/BCJ20170541

    Onconase® (ONC), extracted by the oocytes of the frog Rana Pipiens , is a monomeric member of the secretory "pancreatic-type" RNase super-family. Interestingly, ONC is the only monomeric ribonuclease endowed with a high cytotoxic activity. In contrast to other monomeric RNases, ONC displays a high cytotoxic activity. In this work, we found that ONC spontaneously forms dimeric traces and that the dimer amount increases of about four times after lyophilization from acetic acid solutions. Differently from RNase A and the bovine seminal ribonuclease (BS-RNase), which produce N- and C-terminal domain-swapped conformers, ONC forms only one dimer, here named ONC-D. Cross-linking with divinylsulfone reveals that this dimer forms through the three-dimensional domain swapping (3D-DS) of its N-termini, being the C-termini blocked by a disulfide bond. Also, an homology model is proposed for ONC-D, starting from the well-known structure of RNase A N-swapped dimer and taking into account the results obtained from spectroscopic and stability analyses. Finally, we show that ONC is more cytotoxic and exerts a higher apoptotic effect in the dimeric rather than in its monomeric form, either when administered alone or when accompanied by the chemotherapeutic drug gemcitabine. These results suggest new promising implications in cancer treatment.

  • A comparison study on RNase A oligomerization induced by cisplatin, carboplatin and oxaliplatin.

    Publication Date: 09/05/2017 on Journal of inorganic biochemistry
    by Picone D, Donnarumma F, Ferraro G, Gotte G, Fagagnini A, Butera G, Donadelli M, Merlino A
    DOI: 10.1016/j.jinorgbio.2017.05.005

    Cisplatin (CDDP) can form interprotein cross-links, leading to the formation of platinated oligomers. A dimer, a trimer and higher oligomers of bovine pancreatic ribonuclease (RNase A) obtained upon reaction with CDDP in 1:10 protein to metal ratio at 37°C have been previously characterized. Here, we verify the ability of carboplatin and oxaliplatin to induce RNase A oligomerization under the same experimental conditions. The amount of formed RNase A oligomers was compared with that obtained in the reaction of the protein with CDDP. Among the three anticancer agents, CDDP is the most reactive and the most effective in inhibiting the ribonucleolytic activity of the protein. Oxaliplatin is the least potent oligomerization agent. Biophysical characterizations of structure and stability of platinated dimers formed in the presence of carboplatin and oxaliplatin suggest that they have a similar thermal stability and are more prone to dissociation than the corresponding dimer obtained with CDDP. Oligomers obtained in the presence of carboplatin are the most active. X-ray structures of the monomeric adducts that RNase A forms with the three drugs provide a rational basis to explain the different effects of the three anticancer agents on enzymatic activity and protein aggregation. Although platinated oligomers of RNase A formed upon reaction with CDDP, carboplatin and oxaliplatin retain a residual ribonuclease activity, they do not show cytotoxic action, suggesting that protein aggregation processes induced by Pt-based drugs can represent a collateral drawback, which affects the functional state of protein targets and reduces the efficacy of Pt-based drug treatment.

  • Ecotoxicological survey of MNEI and Y65R-MNEI proteins as new potential high-intensity sweeteners.

    Publication Date: 01/04/2017 on Environmental science and pollution research international
    by Rega MF, Siciliano A, Gesuele R, Lofrano G, Carpentieri A, Picone D, Guida M
    DOI: 10.1007/s11356-017-8626-0

    Low-calorie sweeteners are widespread. They are routinely introduced into commonly consumed food such as diet sodas, cereals, and sugar-free desserts. Recent data revealed the presence in considerable quantities of some of these artificial sweeteners in water samples qualifying them as a class of potential new emerging contaminants. This study aimed at evaluating the ecotoxicity profile of MNEI and Y65R-MNEI, two engineered products derived from the natural protein monellin, employing representative test organism such as Daphnia magna, Ceriodaphnia dubia, and Raphidocelis subcapitata. Potential genotoxicity and mutagenicity effects on Salmonella typhimurium (strain TA97a, TA98, TA100, and TA1535) and Escherichia coli (strain WP2 pkM101) were evaluated. No genotoxicity effects were detected, whereas slight mutagenicity was highlighted by TA98 S. typhimurium. Ecotoxicity results evidenced effects approximately up to 14 and 20% with microalgae at 500 mg/L of MNEI and Y65R-MNEI, in that order. Macrophytes and crustaceans showed no significant effects. No median effective concentrations were determined. Overall, MNEI and Y65R-MNEI can be classified as not acutely toxic for the environment.

  • A preliminary study on the application of natural sweet proteins in agar-based gels.

    Publication Date: 01/04/2017 on Journal of texture studies
    by Miele NA, Di Monaco R, Dell'Amura F, Rega MF, Picone D, Cavella S
    DOI: 10.1111/jtxs.12215

    Natural sweet proteins may be used as sugar replacer in simple liquid food systems but their applicability in more complex matrices has not been investigated yet. Gelling agent nature and texture characteristics as well as type and distribution of a stimulus in a gel could affect taste perception through inhibition or enhancement of tastants migration to the receptors. The mechanical, nonoral texture and time-intensity sweetness characteristics of sweet proteins MNEI and super sweet Y65R mutant, aspartame and saccharin added at a concentration iso-sweet to 40 g/L of sucrose in three agar gel concentrations (1%, 1.5%, and 2%) were evaluated. The results have shown that agar concentration and agar sweetener interaction particularly affect mechanical fracture stress and non oral hardness of the sweetened gels. Time intensity results illustrated that unlike in solution, the intensity of sweet taste in a gelled system over time decreases. Indeed, the behavior of the sweet proteins differed greatly in the gelled system compared to when they are in solution.

  • Hot spot mapping of protein surfaces with TEMPOL: Bovine pancreatic RNase A as a model system.

    Publication Date: 01/02/2017 on Biochimica et biophysica acta
    by Niccolai N, Morandi E, Gardini S, Costabile V, Spadaccini R, Crescenzi O, Picone D, Spiga O, Bernini A
    DOI: 10.1016/j.bbapap.2016.11.014

    TEMPOL spin-label has been used to identify surface exposure of protein nuclei from NMR analysis of the induced paramagnetic relaxation enhancements (PRE). The absence of linear dependence between atom depths and observed PRE reveals that specific mechanisms drive the approach of the paramagnet to the protein surface. RNase A represents a unique protein system to explore the fine details of the information offered by TEMPOL induced PRE, due to the abundance of previous results, obtained in solution and in the crystal, dealing with surface dynamics behavior of this protein. MD simulations in explicit solvent have been performed, also in the presence of TEMPOL, in order to delineate the role of intermolecular hydrogen bonds (HB) on PRE extents. Comparison of our results with the ones obtained from multiple solvent crystal structure (MSCS) studies yields information on the specificities that these two techniques have for characterizing protein-ligand interactions, a fundamental step in the development of reliable surface druggability predictors.

  • NMR Spectroscopic Assignment of Backbone and Side-Chain Protons in Fully Protonated Proteins: Microcrystals, Sedimented Assemblies, and Amyloid Fibrils.

    Publication Date: 12/12/2016 on Angewandte Chemie (International ed. in English)
    by Stanek J, Andreas LB, Jaudzems K, Cala D, Lalli D, Bertarello A, Schubeis T, Akopjana I, Kotelovica S, Tars K, Pica A, Leone S, Picone D, Xu ZQ, Dixon NE, Martinez D, Berbon M, El Mammeri N, Noubhani A, Saupe S, Habenstein B, Loquet A, Pintacuda G
    DOI: 10.1002/anie.201607084

    We demonstrate sensitive detection of alpha protons of fully protonated proteins by solid-state NMR spectroscopy with 100-111 kHz magic-angle spinning (MAS). The excellent resolution in the Cα-Hα plane is demonstrated for 5 proteins, including microcrystals, a sedimented complex, a capsid and amyloid fibrils. A set of 3D spectra based on a Cα-Hα detection block was developed and applied for the sequence-specific backbone and aliphatic side-chain resonance assignment using only 500 μg of sample. These developments accelerate structural studies of biomolecular assemblies available in submilligram quantities without the need of protein deuteration.