Succinylhydroxamic derivatives of alpha-amino acids as MMP inhibitors. Study of complex-formation equilibria with Cu2+, Ni2+ and Zn2+

A series of Pro- and Phe-succinyl hydroxamate derivatives, whose nanomolar inhibitory activity towards a series of matrix metalloproteinases (MMPs) was previously reported, have been studied and described herein in their interaction with Cu(2+), Zn(2+), Ni(2+) in aqueous solution, by using potentiometric, spectroscopic and ESI-MS (electrospray ionization mass) spectrometric techniques. A systematic study at various ligand-to-metal molar ratios allowed the determination of the stability constants of the complexes as well as the estimation of the coordination modes. The similarity in the biological activity of these compounds seems to be paralleled by the identical metal-complexation behaviour at neutral pH, namely in terms of chelating effectiveness and coordination modes, irrespective of the presence of one carboxylic or hydroxamate as extra groups, or also of the type of amino-acid residue at the other flank of the succinyl chain, which seems to be enough away from the succinyl hydroxamate metal-binding group. The stability order of the metal complexes with these ligands follows the Irving-Williams trend for this type of complex systems. Noteworthy is the identification of an interesting pentanuclear copper(II) species with the monohydroxamic ligands which structure was ascribed to a 12-metallacrown-4.     

Venous blood lactate evaluation in equine neonatal intensive care

The use of blood lactate concentration as an indicator of prognosis and disease severity has become a common practice in equine medicine, especially with the validation of handheld analyzers. However, few authors described lactate concentration in critically ill foals, and there are no published studies about the use of handheld analyzers in neonatal foals. In this study, for the first time in the equine neonate, we validated the Lactate Scout analyzer, both in healthy and in critically ill foals. The study also describes the normal range for blood lactate in 26 healthy neonatal foals during the first 72 h of life. Moreover, the utility of venous lactate measurement in 88 critically ill foals was determined, describing lactate values in the most common neonatal pathologies, evaluating serial blood lactate measurements, and investigating its prognostic value. The comparison with the enzymatic-colorimetric reference method showed that the Lactate Scout analyzer is reliable. The mean difference (bias ±2SD) between the two methods was close to zero for all comparisons, and the SD of difference was ±0.76 with a 95% confidence interval from −1.58 to 1.40 mmol/L. In healthy foals, blood lactate concentrations at birth and at 12 h of life were statistically higher (P < 0.01) than lactate concentrations measured at subsequent times. In critically ill foals, the highest lactate concentration at admission was found in hemorrhagic shock, septic shock, and complicated perinatal asphyxia syndrome (PAS). Our results showed that hyperlactatemia, although it does not provide diagnostic information, indicates the severity of illness and the need for an early and aggressive intervention. This could be very useful both during hospitalization and in the field to support veterinarians in making a decision about referral. Furthermore lactatemia proved to be a reliable prognostic parameter: In nonsurviving foals, hyperlactatemia persisted during the entire hospitalization, whereas in survivors there were no significant differences after 24 h from admission. Because prognostic parameters have certain limitations, hyperlactatemia should not be used alone to decide whether to discontinue treatments in critically ill foals. A careful and complete clinical examination is always essential.     

Acid gel formation in (pseudo) alginates with and without G blocks produced by epimerising mannuronan with C5 epimerases

The main scope of this paper is the characterization, in terms of viscoelastic and mechanical properties, of acid gels formed from solutions of mannuronan ALG (0%G/0%GG) and its enzymatically epimerised products. The epimerised products were obtained using recombinantly produced mannuronan C5 epimerases named AlgE1 and AlgE4, which catalyse the conversion of mannuronic residues into guluronic (G) and guluronic–mannuronic (GM) blocks, respectively. The products used in this study resulted from either the action of AlgE1 on mannuronan for 5 and 24 h (named ALG(44%G/32%GG) and ALG (68%G/59%GG), respectively) or AlgE4 on mannuronan (named ALG (47%G/0%GG)). d-gluconic acid-δ-lactone (GDL) was used as H⁺-donor to produce acidic gels. ALG (0%G/0%GG) yields strong, stable solid-like structures. As predicted by circular dichroism measurements performed at different pH, gelation of ALG (47%G/0%GG) occurs at lower values of pH (1) than those obtainable using GDL. Hydrochloric acid was therefore added to ALG (47%G/0%GG) solutions yielding rapid sol–gel transitions and gels with a remarkable resistance to thermal treatment.

The introduction of guluronic residues along the chain (ALG (44%G/32%GG)) causes a reduction in the storage modulus at the equilibrium with respect to that of ALG (0%G/0%GG) and the occurrence of negligible syneresis at the highest polymer concentrations. The increase in the average length of the G blocks (ALG (68%G/59%GG)) is accompanied by a further increase in the storage modulus without the occurrence of any significant syneresis.     

Enzymatic cross-linking versus radical polymerization in the preparation of gelatin PolyHIPEs and their performance as scaffolds in the culture of hepatocytes

Highly open porous biodegradable scaffolds, based on gelatin A3, were fabricated with the aim of using them for tissue-engineering applications. The fabrication process is based on an emulsion-templating technique. In the preparation of gelatin scaffolds two different cross-linking procedures were adopted: (I) radical polymerization of the methacrylate functionalities, previously introduced onto the gelatin chains and (II) formation of isopeptide bridges among the gelatin chains promoted by the enzyme microbial transglutaminase. The method of cross-linking exerts a pronounced effect on the morphology of the porous biomaterials: radical polymerization of methacrylated gelatin allowed the production of scaffolds with a better defined porous structure, while the enzymatically cross-linked scaffolds were characterized by a thinner skeletal framework. A suitable sample of each kind of the differently cross-linked porous biomaterials was tested for the culture of hepatocytes. The scaffold obtained by radical polymerization possessed a morphology characterized by relatively large voids and interconnects, and as a consequence, it was more suitable for hepatocytes colonization. On the other hand, the enzymatically cross-linked scaffold resulted in less cytotoxicity and the cultured hepatocytes expressed a better differentiated phenotype, as evidenced by a greater expression and more correct localization of key adhesion proteins.     

C6-oxidation and c5-epimerization of locust bean galactomannan studied by high field NMR and circular dichroism

Galactose depleted locust bean gum was selectively oxidized in C(6) position and epimerized with mannuronan C(5)-epimerases to obtain the corresponding artificial uronanes. These new pseudo-alginates were characterized by NMR spectroscopy and circular dichroism (CD). Specifically, 1D and 2D NMR techniques allowed the degree of epimerization, the distribution of mannuronic and guluronic acid residues in the polysaccharidic chain, and the average G block length to be determined. In addition, NMR diffusion experiments showed that the epimerization reaction did not significantly degrade the polysaccharidic chains. Circular dichroism was used to investigate the kinetics of the epimerization reaction and to evidence the specific interaction between the epimerized locust bean samples with Ca(II) ions in dilute solution. All of the samples considered in this study form wall to wall gels in concentrated polymer solutions.     

SEC23-SEC31 the interface plays critical role for export of procollagen from the endoplasmic reticulum

COPII proteins are essential for exporting most cargo molecules from the endoplasmic reticulum. The membrane-facing surface of the COPII proteins (especially SEC23-SEC24) interacts directly or indirectly with the cargo molecules destined for exit. As we characterized the SEC23A mutations at the SEC31 binding site identified from patients with cranio-lenticulo-sutural dysplasia, we discovered that the SEC23-SEC31 interface can also influence cargo selection. Remarkably, M702V SEC23A does not compromise COPII assembly, vesicle size, and packaging of cargo molecules into COPII vesicles that we have tested but induces accumulation of procollagen in the endoplasmic reticulum when expressed in normal fibroblasts. We observed that M702V SEC23A activates SAR1B GTPase more than wild-type SEC23A when SEC13-SEC31 is present, indicating that M702V SEC23A causes premature dissociation of COPII from the membrane. Our results indicate that a longer stay of COPII proteins on the membrane is required to cargo procollagen than other molecules and suggest that the SEC23-SEC31 interface plays a critical role in capturing various cargo molecules.