Trick or treat? Muslim Thangals, psychologisation and pragmatic realism in Northern Kerala, India

Thangals are an endogamous community in Kerala, India, of Yemeni heritage who claim direct descent from the Prophet Muhammad’s family. Due to their sacrosanct status, many thangals work as religious healers and thus are part of the informal mental health care system in Northern Kerala. Using the case of one thangal healer as an illustration of the many ritual healers in Kerala who engage the modern discourse of psychology in their practices, I argue that the psychologisation of ritual healing is part of a wider trend: the increasing rationalisation and scientification of traditional medical practices, whereby an increasing number of traditional healers negotiate science, modernity and religion and position their practice within these contested fields. Based on the analysis of this thangal’s healing practice in the local context of Northern Kerala, I further argue that in order to understand “ritual” healing, scholars should emphasise pragmatic realism more than doctrinal purity

Experimental observation of double-walled peptide nanotubes and monodispersity modeling of the number of walls

Self-assembled nanoarchitectures based on biological molecules are attractive because of the simplicity and versatility of the building blocks. However, size control is still a challenge. This control is only possible when a given system is deeply understood. Such is the case with the lanreotide acetate, an octapeptide salt that spontaneously forms monodisperse nanotubes when dissolved into pure water. Following a structural approach, we have in the past demonstrated the possibility to tune the diameter of these nanotubes while keeping a strict monodispersity, either by chemical modification of one precise amino acid on the peptide sequence or by changing the size of the counterions. On the basis of these previous studies, we replaced monovalent counterions by divalent ones to vary the number of walls. Indeed, in the present work, we show that lanreotide associated with a divalent counterion forms double-walled nanotubes while keeping the average diameter constant. However, the strict monodispersity of the number of walls was unexpected. We propose that the divalent counterions create an adhesion force that can drive the wall packing. This adhesion force is counterbalanced by a mechanical one that is related to the stiffness of the peptide wall. By taking into account these two opposite forces, we have built a general model that fully explains why the lanreotide nanotubes formed with divalent counterions possess two walls and not more

Structural role of counterions adsorbed on self-assembled peptide nanotubes

Among noncovalent forces, electrostatic ones are the strongest and possess a rather long-range action. For these reasons, charges and counterions play a prominent role in self-assembly processes in water and therefore in many biological systems. However, the complexity of the biological media often hinders a detailed understanding of all the electrostatic-related events. In this context, we have studied the role of charges and counterions in the self-assembly of lanreotide, a cationic octapeptide. This peptide spontaneously forms monodisperse nanotubes (NTs) above a critical concentration when solubilized in pure water. Free from any screening buffer, we assessed the interactions between the different peptide oligomers and counterions in solutions, above and below the critical assembly concentration. Our results provide explanations for the selection of a dimeric building block instead of a monomeric one. Indeed, the apparent charge of the dimers is lower than that of the monomers because of strong chemisorption. This phenomenon has two consequences: (i) the dimer-dimer interaction is less repulsive than the monomer-monomer one and (ii) the lowered charge of the dimeric building block weakens the electrostatic repulsion from the positively charged NT walls. Moreover, additional counterion condensation (physisorption) occurs on the NT wall. We furthermore show that the counterions interacting with the NTs play a structural role as they tune the NTs diameter. We demonstrate by a simple model that counterions adsorption sites located on the inner face of the NT walls are responsible for this size control

Christianisme et islam en milieu indou Pratiques et debats

Available from INIST (FR), Document Supply Service, under shelf-number : AR 16493 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEMinistere de la Recherche et de l'Espace (MRE), 75 - Paris (France)FRFranc