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Aldaric acids are becoming valuable platform chemicals in bioeconomy and circular economy approaches. Among them, mucic acid (meso-galactaric acid) is gaining industrial attention as a bio-based precursor of adipic acid found in polyamides, and of 2,5-furan dicarboxylic acid, a valuable substitute for terephthalic acid in polyesters. A combination of detailed experimental protocols and conditions with DFT computational calculations for the synthesis of mucic acid from galactose are herein described. The product is obtained by reaction with diluted aqueous nitric acid as the oxidizing agent and the reaction medium. Optimized reaction conditions require 5 M nitric acid, 95 °C, galactose/HNO3 molar ratio 1 : 9, 100 g/L galactose concentration in the reaction medium. Computational calculations suggest that the oxidation mechanism may involve a contextual oxygen protonation and nitrate nucleophilic attack, leading to the oxidized product. The proposed mechanism requires a stoichiometry of 6 moles of nitric acid per galactose mole, albeit both experimental and computational data evidence that proton excess may be necessary to start the reaction. The reported study gives useful insights for the production of galactaric acid.

The present study reports on the synthesis of a new alkoxysilane-bearing light-responsive cinnamyl group and its application as a surface functionalization agent for the development of SiO2 nanoparticles (NPs) with photoreversible tails. In detail, cinnamic acid (CINN) was activated with N-hydroxysuccinimide (NHS) to obtain the corresponding NHS-ester (CINN-NHS). Subsequently, the amine group of 3-aminopropyltriethoxysilane (APTES) was acylated with CINN-NHS leading to the generation of a novel organosilane, CINN-APTES, which was then exploited for decorating SiO2 NPs. The covalent bond to the silica surface was confirmed by solid state NMR, whereas thermogravimetric analysis unveiled a functionalization degree much higher compared to that achieved by a conventional double-step post-grafting procedure. In light of these intriguing results, the strategy was successfully extended to naturally occurring sepiolite fibers, widely employed as fillers in technological applications. Finally, a preliminary proof of concept of the photoreversibility of the obtained SiO2@CINN-APTES system has been carried out through UV diffuse reflectance. The overall outcomes prove the consistency and the versatility of the methodological protocol adopted, which appears promising for the design of hybrid NPs to be employed as building blocks for photoresponsive materials with the ability to change their molecular structure and subsequent properties when exposed to different light stimuli.

Gelatin is a costless polypeptide material of natural origin, able to form hydrogels that are potentially useful in biomaterial scaffold design for drug delivery, cell cultures, and tissue engineering. However, gelatin hydrogels are unstable at physiological conditions, losing their features only after a few minutes at 37 °C. Accordingly, treatments to address this issue are of great interest. In the present work, we propose for the first time the use of bi- and trifunctional tetrazoles, most of them unknown to date, for photoinduced gelatin cross-linking towards the production of physiologically stable hydrogels. Indeed, after UV-B irradiation, aryl tetrazoles generate a nitrilimine intermediate that is reactive towards different functionalities, some of them constitutively present in the amino acid side chains of gelatin. The efficacy of the treatment strictly depends on the structure of the cross-linking agent used, and substantial improved stability was observed by switching from bifunctional to trifunctional cross-linker

Contesto scientifico. I glicani rivestono un ruolo cruciale nel sistema nervoso centrale (SNC) e il loro studio è fondamentale per un'accurata comprensione della neurochimica, ma la conoscenza scientifica riguardo ai glicani presenti nel SNC è ancora limitata. Lo scopo di questa tesi è fornire nuovi strumenti al glicochimico e al glicoanalista per condurre studi di neurochimica, funzionali all'esplorazione del ruolo dei glicani nel SNC. Questa tesi presenta un nuovo metodo analitico per lo studio degli N-glicani da tessuti cerebrali (LSD); lo stato dell'arte di un lavoro in corso riguardante l'investigazione di N-glicani e N-glicoproteine differentemente espresse in tessuti cerebrali appartenenti a diverse specie; un efficiente metodo di marcatura chimica per (glico)proteine, applicato con successo a una N-glicoproteina, Neuroserpina (NS), che polimerizza nel SNC con conseguenze patologiche; e le sintesi di glicosidi e glicodendrimeri con potenziali applicazioni in studi neurochimici. Metodi. LSD si sviluppa a partire dalla lisi chimica di tessuti cerebrali (tc), con conseguente precipitazione del proteoma (i.e., metanolo/cloroformio), deglicosilazione enzimatica (i.e., PNGase F), purificazione degli N-glicani, marcatura chimica (i.e., amminazione riduttiva su N-acetilglucosammina terminale) e analisi tramite approcci LC-MS. LSD è stato ottimizzato su campioni di tc e accuratamente validato (i.e., sensibilità, precisione, linearità, range dinamico, selettività, robustezza). L'analisi degli N-glicani è stata anche effettuata tramite deglicosilazione enzimatica in-gel da elettroforesi di proteine, mentre un protocollo di digestione con Tripsina in-gel è stato usato per l'identificazione di N-glicoproteine e siti di N-glicosilazione tramite approcci LC-MS su peptidi. NS è stata dimetilata chimicamente (i.e., amminazione riduttiva su lisina), nella sua forma monomerica (mhNS) e polimerica (phNS) e l'esito della reazione è stato valutato tramite MS, per l'inve, Background. Glycans play crucial roles within the central nervous system (CNS) and their study is essential for a thorough comprehension of neurochemistry, but the scientific knowledge about CNS glycans remains scarce. The aim of this thesis is to provide the glycochemist and glycoanalyst with novel tools for neurochemistry studies, towards the exploration of glycan roles in the CNS. This thesis presents a novel analytical method for brain N-glycans investigation (LSD); the state of the art of an ongoing work for the investigation of N-glycans and N-glycoproteins differentially expressed in brain tissues of different species; an efficient chemical labelling method for (glyco)proteins, successfully applied on Neuroserpin (NS), a pathologically-polymerising CNS N-glycoprotein; and the syntheses of glycosides and glycodendrimers with potential room for neuromedical studies. Methods. LSD comprised brain tissue (bt) chemical lysis, proteome precipitation (i.e., methanol/chloroform), enzymatic deglycosylation (i.e., PNGase F), N-glycans purification, chemical labelling (i.e., reductive amination on terminal N-acetylglucosamine), and LC-MS bioanalysis. The method has been optimised on bt and thoroughly validated (i.e., sensitivity, precision, linearity, range, selectivity, robustness). N-glycans analysis has also been carried out through protein electrophoresis in-gel deglycosylation, while in-gel trypsinisation was used for the LC-MS identification of N-glycoproteins and N-glycosylation sites. NS has been dimethylated (i.e., reductive amination on lysine) in its monomeric (mhNS) and polymeric (phNS) forms, and the reaction outcome has been evaluated using MS, towards the investigation of NS polymerisation-driving molecular features. Glycosides were synthesised with a Fischer- type glycosylation reaction on unprotected monosaccharides using either allyl alcohol or decenol as glycosyl acceptors, while glycodendrimers were obtained decorating olefin-metathesis-synthesised de

The ability of gelatin-based hydrogels of incorporating and releasing under controlled conditions 5,6-dihydroxyindole-2-carboxylic acid (DHICA), a melanin-related metabolite endowed with marked antioxidant properties was investigated. The methyl ester of DHICA, MeDHICA, was also tested in view of its higher stability, and different solubility profile. Three types of gelatin-based hydrogels were prepared: pristine porcine skin type A gelatin (HGel-A), a pristine gelatin cross-linked by amide coupling of lysines and glutamic/aspartic acids (HGel-B), and a gelatin/chitosan blend (HGel-C). HGel-B and HGel-C differed in the swelling behavior, showed satisfactorily high mechanical strength at physiological temperatures and well-defined morphology. The extent of incorporation into all the gelatins tested using a 10% w/w indole to gelatin ratio was very satisfactory ranging from 60 to 90% for either indoles. The kinetics of indole release under conditions of physiological relevance was evaluated up to 72 h. The highest values were obtained with HGel-B and HGel-C for MeDHICA (90% after 6 h), and an appreciable release was observed for DHICA reaching 30% and 40% at 6 h for HGel-B and HGel-C, respectively. At 72 h, DHICA and MeDHICA were released at around 30% from HGel-A at pH 7.4, with an increase up to 40% at pH 5.5 in the case of DHICA. DHICA incorporated into HGel-B proved fairly stable over 6 h whereas the free compound at the same concentration was almost completely oxidized. The antioxidant power of the indole loaded gelatins was monitored by chemical assays and proved unaltered even after prolonged storage in air, suggesting that the materials could be prepared in advance with respect to their use without alteration of their efficacy.