Pilar Diarte Blasco

Molecular recognition of complex-type biantennary N-glycans by protein receptors: a three-dimensional view on epitope selection by NMR.

The current surge in defining glycobiomarkers by applying lectins rekindles interest in definition of the sugar-binding sites of lectins at high resolution. Natural complex-type N-glycans can present more than one potential binding motif, posing the question of the actual mode of interaction when interpreting, for example, lectin array data. By strategically combining N-glycan preparation with saturation-transfer difference NMR and modeling, we illustrate that epitope recognition depends on the structural context of both the sugar and the lectin (here, wheat germ agglutinin and a single hevein domain) and cannot always be predicted from simplified model systems studied in the solid state. We also monitor branch-end substitutions by this strategy and describe a three-dimensional structure that accounts for the accommodation of the α2,6-sialylated terminus of a biantennary N-glycan by viscumin. In addition, we provide a structural explanation for the role of terminal α2,6-sialylation in precluding the interaction of natural N-glycans with lectin from Maackia amurensis . The approach described is thus capable of pinpointing lectin-binding motifs in natural N-glycans and providing detailed structural explanations for lectin selectivity.

Direct Enzymatic Branch-End Extension of Glycocluster-Presented Glycans: An Effective Strategy for Programming Glycan Bioactivity

The sequence of a glycan and its topology of presentation team up to determine the specificity and selectivity of recognition by saccharide receptors (lectins). Structure-activity analysis would be furthered if the glycan part of a glycocluster could be efficiently elaborated in situ while keeping all other parameters constant. By using a bacterial α2,6-sialyltransferase and a small library of bi- to tetravalent glycoclusters, we illustrate the complete conversion of scaffold-presented lactoside units into two different sialylated ligands based on N-acetyl/glycolyl-neuraminic acid incorporation. We assess the ensuing effect on their bioactivity for a plant toxin, and present an analysis of the noncovalent substrate binding contacts that the added sialic acid moiety makes to the lectin. Enzymatic diversification of a scaffold-presented glycan can thus be brought to completion in situ, offering a versatile perspective for rational glycocluster engineering.

Recent advances on the application of NMR methods to study the conformation and recognition properties of carbohydrates

This report gathers selected and recent examples of studies of the conformation, structure, dynamics and binding features of saccharides and analogues. It has not been our intention to be exhaustive, since many groups are working in this field either on a regular basis or making frequent contributio...

Spolia et Hispania: alcuni esempi Peninsulari

Progressive loss of Roman utilitarian buildings and public complexes, as well as their later reuse were one of the essential features of the urban transformation during Late Antiquity. The phenomenon that followed this process was the spoliation of both constructive and decorative materials. In Roman Hispania the reuse of public buildings affected most of the mainland cities, especially from the 4th c. The emergence of this practice can be traced in the weakening of the local institutions and the administration, but mostly in the rise of Christianity. The new religion stimulated building activities, which resulted in dismantling of the ancient buildings for the construction of new ones. Although the spoliation is easy to identify, it raises many questions. With the aim to answer some of them, and to identify possible common characteristics of the same process that later lead to the emergence of the medieval town, the authors give an overview and the interpretation of the important examples of spolia in Hi...

La percepción del espacio en el urbanismo tardoantiguo: características evolutivas en el ejemplo hispano

Roman urbanism experimented, in Late Antiquity, a fundamental transformation of its structural principles and organisation of space. However, the process - the context in which it took place and its phases - is currently imprecise and its guidelines remain difficult to determine. Taking the Iberian Peninsula as a case study, this article analyses the variants of these transformations, which seemed to be partially perceived by contemporary citizens. Moreover, and following our investigation of Hispanic urban centres, the article outlines the elements that define the characteristics of the Late Antique city and its projection onto the social imaginary: first, a different assessment of urban space, and secondly, a new conception of the horizontal and vertical lines of the construction project of cities.

Redefining the Urban Landscape in Hispania: Entertainment Buildings and their Transformations in Late Antiquity

The transformations of public spaces in Hispanic cities between the third and the sixth century are the theme of this paper. Entertainment buildings are undoubtedly one of the most characteristic elements of the classical Roman cities. Indeed, theatres, amphitheatres and circuses are fundamental to our perception of them.The processes of transformation of these major buildings in Late Antiquity, which varied in some aspects according to specific characteristics, had in common a general trend in the dismantling of part of its architecture and, above all, the growth of private use and of spoliation. The mutations that occurred in the late classical urban fabric were the beginning of a process that continued, in some cases, with the establishment of burial areas and, more rarely, with the appearance of Christian buildings. The wider ‘topographic Christianization’ took place once the classical city was already dissolved or, at least, immersed in that evolution. This paper identifies that this process did not ...