Geometry of Miura-folded metamaterials.

This paper describes two folded metamaterials based on the Miura-ori fold pattern. The structural mechanics of these metamaterials are dominated by the kinematics of the folding, which only depends on the geometry and therefore is scale-independent. First, a folded shell structure is introduced, where the fold pattern provides a negative Poisson's ratio for in-plane deformations and a positive Poisson's ratio for out-of-plane bending. Second, a cellular metamaterial is described based on a stacking of individual folded layers, where the folding kinematics are compatible between layers. Additional freedom in the design of the metamaterial can be achieved by varying the fold pattern within each layer.

A DNA nanomachine induced by single-walled carbon nanotubes on gold surface

Single-walled carbon nanotubes (SWNTs) can selectively induce human telomeric i-motif DNA formation at pH 7.0. Based on this property, we design a DNA nanomachine induced by SWNTs on gold surface. The motor DNA is human telomeric G-quadruplex DNA. The reversible hybridization between the motor DNA and its complementary human telomeric i-motif DNA can be modulated by SWNTs without changing solution pH. Up to now, to our knowledge, there is no report to show that a DNA nanomachine is induced by SWNTs or a DNA nanomachine can detect i-motif formation at pH 7.0. Our work may provide a new concept for designing an SWNT-induced DNA nanomachine and for the detection of i-motif DNA structure at pH 7.0. DNA hybridization, conformational transition and i-motif formation have been characterized on surface or in solution by fluorescence confocal microscopy, circular dichroism, DNA melting and gel electrophoresis. The folding and unfolding kinetics of the DNA nanomachine on gold surface were studied by Fourier transform-surface plasmon resonance (FT-SPR). All these results indicate that SWNTs can induce the DNA nanomachine to work efficiently and reversibly.

Differential scanning calorimetry in life science: thermodynamics, stability, molecular recognition and application in drug design

All biological phenomena depend on molecular recognition, which is either intermolecular like in ligand binding to a macromolecule or intramolecular like in protein folding. As a result, understanding the relationship between the structure of proteins and the energetics of their stability and binding with others (bio)molecules is a very interesting point in biochemistry and biotechnology. It is essential to the engineering of stable proteins and to the structure-based design of pharmaceutical ligands. The parameter generally used to characterize the stability of a system (the folded and unfolded state of the protein for example) is the equilibrium constant (K) or the free energy (deltaG(o)), which is the sum of enthalpic (deltaH(o)) and entropic (deltaS(o)) terms. These parameters are temperature dependent through the heat capacity change (deltaCp). The thermodynamic parameters deltaH(o) and deltaCp can be derived from spectroscopic experiments, using the van't Hoff method, or measured directly using calorimetry. Along with isothermal titration calorimetry (ITC), differential scanning calorimetry (DSC) is a powerful method, less described than ITC, for measuring directly the thermodynamic parameters which characterize biomolecules. In this article, we summarize the principal thermodynamics parameters, describe the DSC approach and review some systems to which it has been applied. DSC is much used for the study of the stability and the folding of biomolecules, but it can also be applied in order to understand biomolecular interactions and can thus be an interesting technique in the process of drug design.

Structural and Molecular Biology of Type I Galactosemia: Disease-associated Mutations

Type I galactosemia results from reduced galactose 1-phosphate uridylyltransferase (GALT) activity. Signs of disease include damage to the eyes, brain, liver, and ovaries. However, the exact nature and severity of the pathology depends on the mutation(s) in the patient's genes and his/her environment. Considerable enzymological and structural knowledge has been accumulated and this provides a basis to explain, at a biochemical level, impairment in the enzyme in the more than 230 disease-associated variants, which have been described. The most common variant, Q188R, occurs close to the active site and the dimer interface. The substitution probably disrupts both UDP-sugar binding and homodimer stability. Other alterations, for example K285N, occur close to the surface of the enzyme and most likely affect the folding and stability of the enzyme. There are a number of unanswered questions in the field, which require resolution. These include the possibility that the main enzymes of galactose metabolism form a supramolecular complex and the need for a high resolution crystal structure of human GALT. (C) 2011 IUBMB IUBMB Life, 63(11): 949-954, 2011

Using sketch-map coordinates to analyze and bias molecular dynamics simulations

When examining complex problems, such as the folding of proteins, coarse grained descriptions of the system drive our investigation and help us to rationalize the results. Oftentimes collective variables (CVs), derived through some chemical intuition about the process of interest, serve this purpose. Because finding these CVs is the most difficult part of any investigation, we recently developed a dimensionality reduction algorithm, sketch-map, that can be used to build a low-dimensional map of a phase space of high-dimensionality. In this paper we discuss how these machine-generated CVs can be used to accelerate the exploration of phase space and to reconstruct free-energy landscapes. To do so, we develop a formalism in which high-dimensional configurations are no longer represented by low-dimensional position vectors. Instead, for each configuration we calculate a probability distribution, which has a domain that encompasses the entirety of the low-dimensional space. To construct a biasing potential, we exploit an analogy with metadynamics and use the trajectory to adaptively construct a repulsive, history-dependent bias from the distributions that correspond to the previously visited configurations. This potential forces the system to explore more of phase space by making it desirable to adopt configurations whose distributions do not overlap with the bias. We apply this algorithm to a small model protein and succeed in reproducing the free-energy surface that we obtain from a parallel tempering calculation.

Charles Larned letter, April 3, 1813.

Charles Larned (1791-1834) was a lawyer and American military officer who served during the War of 1812. He was the son of Simon Larned (1753-1817), who served as a captain in the Revolutionary War and was a member of the United States Congress from Massachusetts from 1804-1805. Charles studied law in the office of Henry Clay in Kentucky, and was dining with a group of prominent citizens when word was received that General William Henry Harrison could soon be overpowered by General Henry Proctor. Colonel Owen, a member of the group, organized a regiment to reinforce Harrison’s troops. Larned became a member and subsequently survived the River Raisin Massacre and was later present at the Battle of the Thames. He was also part of a group of men who learned of General William Hull’s plan to surrender Detroit to the British and planned to overtake him should this occur. However, the plan failed, Hull did surrender and the men became prisoners of the British. After the war, Larned became a lawyer, and served as Attorney General of Michigan Territory during the Black Hawk War. During the cholera epidemic of 1834, he worked tirelessly to assist others, but was stricken with the disease and died. Letter Transcription: Pittsfield, April 8, 1813 I think that by this time my dear Charles you will allow I have some reason to give you a gentle reprimand for breach of duty—but I will not censure you upon suspicion maybe you have substantial reasons—at any rate one cannot very graciously reproach the other for negligence I for one am healthy as ham & that we have so seldom exchanged letters during your absence & on my honor promise to be a better girl in future—but the truth is my Dear Charles I am secretary for the Family—Mama you know never writes & James but seldom & they are all dispersed in different directions, consequently I have many calls upon my time—this to be sure is a pleasant duty & I urge it only as a slight palliation for my remissness if you should consider it as such—now I have finished my preface—I will try to be more interesting & doubtless I succeed. Our dear Father we hope & trust is now in Green Bush, where he will probably remain a month perhaps & from thence he expects to go to Sacket’s harbor—at which place you know our troops are fast collecting-- We shall hope to see him either here or there before he goes. Brother George I believe is [still] at Plattsburgh but expects soon to be removed to some other military part perhaps with Papa (I hope so at least). We have just got letters from Brothers Sylvester & Joseph at Middlebury—they are in good health. Mama has for some weeks been afflicted with an inflammation in her eyes but seems now to be convalescing. Sister Martha has been somewhat unwell for a few weeks but is now tolerably recovered. James & myself are both in our usual good health & at this time seated by the same stand, one reading, the other writing. Thus my Dear Charles have I given you an abstract history of our Family—but here indeed is a wonderful omission; not a word about Miss Harriet Hunt, who in truth ought to have been noted first but the last she’s not the least in my memory. She is much grown since you saw her, but does not speak as fluently as we could wish—a few word she can say. Probably before this you have been informed of the great loss your friend Sherrill has sustained in the death of his mother—also of the revolution that has taken place in Hackbridge as it respects the religion & morality of the place that more than one hundred on the plain have become religious converts & c—indeed I am at a loss what to say that will afford your pleasure—a narrative at this time must be gloomy indeed. The distressing situation of our country at this time would make almost any recital melancholy. The prevailing epidemic has swept off many of your acquaintance no doubt. Mrs. Dewey of Williamstown, the sister of Mrs. Danforth, has left a Husband, Children & many Friends sincerely to lament her loss—some few have died in our village, but we have escaped astonishingly –it has raged in every town about us--If we are unwilling to acknowledge a God in his mercies. I fear she shall be compelled to do it in the awfulness of his judgments.--------I am much [pleased] with our new neighbors the Parsons Wife & a Miss Woodward her cousin is a fine girl, I think, Mrs. Allen has not a handsome face but something in her manner that interests one her person I think the handsomest I ever saw & the Parson seems well pleased with his selection—Mrs. Ripley is with them this winter & will probably remain thro the summer—Her husband at [Sackett’s Harbor] little or no alteration is apparent since her marriage—she seems as gay & fond of company as ever.-------Mrs. [McKnight] it is expected will commence housekeeping in about three weeks in the house formerly occupied by Mr…. [Report] says that Mr. Goodman & Clarissa Weller are soon to be married & many other things that I must omit to mention for Mama wants a… PS reserved--now my Dear Charles remember you are considerably… & I am confident you have as much leisure as I have –… be ceremonious but write whenever I find time not & I beg… the same – I tell James I shall not send his love for he must write himself. I shall anxiously expect you to write & do not disappoint your affectionate, sister--H One word my Dear Charles from your affectionate Mother who longs to see Her Dear son Charles—but being deprived of that rich blessing at present—begs Him so to conduct that she may hope for it ere long—do you search the Scriptures and keep the Sabbath holy unto the Lord—and all the sacred Commandments of God—it is my ardent desire…He would protect, support and provide for your soul and body and believe me your affectionate friend and Mother. R Larned.

Last will and testament - Peter Wright

The last will and testament of Peter Wright, dated December 18th, 1812. He was the father of Mary Wright, the first wife of Thomas Wilson (third generation). In the will, Peter states his executors as Lawrence Lemon, George Garner, and his wife Susannah Wright. There is also a transcript of the handwritten will.

Charles Larned letter - April 3, 1813

Letter Transcription: Pittsfield, April 8, 1813 I think that by this time my dear Charles you will allow I have some reason to give you a gentle reprimand for breach of duty—but I will not censure you upon suspicion maybe you have substantial reasons—at any rate one cannot very graciously reproach the other for negligence I for one am healthy as ham & that we have so seldom exchanged letters during your absence & on my honor promise to be a better girl in future—but the truth is my Dear Charles I am secretary for the Family—Mama you know never writes & James but seldom & they are all dispersed in different directions, consequently I have many calls upon my time—this to be sure is a pleasant duty & I urge it only as a slight palliation for my remissness if you should consider it as such—now I have finished my preface—I will try to be more interesting & doubtless I succeed. Our dear Father we hope & trust is now in Green Bush, where he will probably remain a month perhaps & from thence he expects to go to Sacket’s harbor—at which place you know our troops are fast collecting-- We shall hope to see him either here or there before he goes. Brother George I believe is [still] at Plattsburgh but expects soon to be removed to some other military part perhaps with Papa (I hope so at least). We have just got letters from Brothers Sylvester & Joseph at Middlebury—they are in good health. Mama has for some weeks been afflicted with an inflammation in her eyes but seems now to be convalescing. Sister Martha has been somewhat unwell for a few weeks but is now tolerably recovered. James & myself are both in our usual good health & at this time seated by the same stand, one reading, the other writing. Thus my Dear Charles have I given you an abstract history of our Family—but here indeed is a wonderful omission; not a word about Miss Harriet Hunt, who in truth ought to have been noted first but the last she’s not the least in my memory. She is much grown since you saw her, but does not speak as fluently as we could wish—a few word she can say. Probably before this you have been informed of the great loss your friend Sherrill has sustained in the death of his mother—also of the revolution that has taken place in Hackbridge as it respects the religion & morality of the place that more than one hundred on the plain have become religious converts & c—indeed I am at a loss what to say that will afford your pleasure—a narrative at this time must be gloomy indeed. The distressing situation of our country at this time would make almost any recital melancholy. The prevailing epidemic has swept off many of your acquaintance no doubt. Mrs. Dewey of Williamstown, the sister of Mrs. Danforth, has left a Husband, Children & many Friends sincerely to lament her loss—some few have died in our village, but we have escaped astonishingly –it has raged in every town about us--If we are unwilling to acknowledge a God in his mercies. I fear she shall be compelled to do it in the awfulness of his judgments.--------I am much [pleased] with our new neighbors the Parsons Wife & a Miss Woodward her cousin is a fine girl, I think, Mrs. Allen has not a handsome face but something in her manner that interests one her person I think the handsomest I ever saw & the Parson seems well pleased with his selection—Mrs. Ripley is with them this winter & will probably remain thro the summer—Her husband at [Sackett’s Harbor] little or no alteration is apparent since her marriage—she seems as gay & fond of company as ever.-------Mrs. [McKnight] it is expected will commence housekeeping in about three weeks in the house formerly occupied by Mr…. [Report] says that Mr. Goodman & Clarissa Weller are soon to be married & many other things that I must omit to mention for Mama wants a… PS reserved--now my Dear Charles remember you are considerably… & I am confident you have as much leisure as I have –… be ceremonious but write whenever I find time not & I beg… the same – I tell James I shall not send his love for he must write himself. I shall anxiously expect you to write & do not disappoint your affectionate, sister--H One word my Dear Charles from your affectionate Mother who longs to see Her Dear son Charles—but being deprived of that rich blessing at present— begs Him so to conduct that she may hope for it ere long—do you search the Scriptures and keep the Sabbath holy unto the Lord—and all the sacred Commandments of God—it is my ardent desire…He would protect, support and provide for your soul and body and believe me your affectionate friend and Mother. R Larned.

Impact de l’expression de l’isoforme p35 de la chaîne invariante humaine chez des souris déficientes en CD74 endogène

La chaîne invariante (Ii ; CD74) est une protéine membranaire de type II qui joue un rôle majeur dans la présentation antigénique. Dans le réticulum endoplasmique (RE), Ii favorise l’assemblage du CMH II et prévient la liaison indésirable de polypeptides. Grâce à son motif di-leucine, la chaîne invariante cible le CMH II dans les endosomes. Une fois dans ces compartiments acides, Ii est dégradé, permettant la liaison de peptides de forte affinité qui seront ensuite présentés aux cellules T CD4+. Chez les souris déficientes en Ii murin (mIi), le CMH II présente une conformation non compacte typique des molécules vides ou liées faiblement à un peptide. Le transport du CMH II est aberrant ce qui conduit à une réduction de son expression en surface ainsi qu’à un défaut de présentation antigénique. De plus, Ii diversifie le répertoire de peptides et assure la sélection thymique des cellules T CD4+. Enfin, il a un rôle dans la maturation des cellules B et les souris déficientes en Ii présentent des nombres réduits de cellules B matures folliculaires (FO). L’isoforme mineure humaine p35 (Iip35) n’existe pas chez la souris et possède une extension cytoplasmique de 16 acides aminés contenant un motif R-x-R de rétention dans le RE. La sortie du RE est conditionnelle à la liaison du CMH II qui permet de masquer le motif de rétention. Iip35 agit comme dominant et impose la rétention aux autres isoformes d’Ii. Cependant, le rôle physiologique du motif R-x-R et, plus globalement, celui d’Iip35, demeurent nébuleux. Pour mieux cerner la fonction d’Iip35, nous avons généré des souris transgéniques (Tg) exprimant l’isoforme humaine Iip35 et avons analysé la conformation et le trafic du CMH II, la sélection thymique et la maturation des cellules B ainsi que la présentation antigénique. Nos résultats ont démontré qu’Iip35 favorise l’assemblage du CMH II dans le RE. Il induit également une conformation compacte du CMH II et augmente l’expression du CMH II en surface. De plus, Iip35 cible le CMH II dans les endosomes où un peptide de forte affinité se lie dans la niche peptidique. Par ailleurs, Iip35 diversifie le répertoire de peptides et rétablit totalement la sélection des cellules T CD4+ ainsi que le niveau d’expression du TCR de ces dernières. Iip35 restaure également la présentation antigénique de l’ovalbumine dont la présentation requiert l’expression d’Ii. Par contre, Iip35 rétablit la présentation des superantigènes mais à un niveau moindre que celui des souris sauvages. Ensuite, Iip35 permet le rétablissement de la sélection des cellules iNKT démontrant qu’il assiste la présentation des lipides par les molécules CD1d. Enfin, les résultats ont démontré qu’Iip35 restaure le développement des cellules B matures folliculaires (FO) mais pas celui des cellules B de la zone marginale. Ceci suggère qu’Iip35 est capable d’induire le développement des cellules FO sans stimulation préalable par le MIF (macrophage migration inhibitory factor). Ainsi, l’ensemble de ces résultats démontre qu’Iip35 est fonctionnel et assure la majorité des fonctions d’Ii. Cependant, Iip35 ne remplace pas mIi endogène concernant la maturation des cellules B MZ suggérant qu’il pourrait avoir un rôle de régulateur.

Ordnung hilffen. Vorreformatorische Geschlechterordnung: Erste deutsche Bibel und Der Ackermann aus Böhmen

Die Dissertation leistet einen Beitrag zur Konstruktion von Geschlechterverhältnissen in der Ehe vor der Reformation. Untersucht werden zwei Texte des 15. Jahrhunderts: Die sogenannte Erste deutsche Bibel (EDB) und die Dichtung Der Ackermann aus Böhmen von Johannes von Tepl. Die Wort-für-Wort-Analyse beider Texte hat aus der zeitgebundenen deutschen Sprachgestalt spezifi-sche Denkfiguren erschlossen. Zentral ist die Gestaltung des Verhältnisses zwischen Gott und Menschen als Rechtsbeziehung Lehen. Das erste Kapitel analysiert und interpretiert die für Ehe- und Geschlechterkonzepte grund-legenden Aussagen von Genesis 1 - 4,1 und den Kanon der fünf Weisheitsbücher der EDB mit folgenden Ergebnissen: 1. Die EDB ist als Rechtsbuch zu lesen, dessen Zentrum die göttliche Herrschaft mit ihrer Rechts-ordnung ist. In diesem Rahmen wird für Mann und Frau die Ordnung Paar definiert. 2. Beide Geschlechter sind gleichwertig. Das kommt in ihren jeweiligen Handlungsfeldern (Werkordnungen) zum Ausdruck. 3. Der Begriff hilffen für die Ehefrau bedeutet Hilfe zum Heil ihres Mannes und eine spezifische Gottesnähe. Dies ist ein entscheidender Unterschied zu Luthers Bibelübersetzung, welche die Frau als untergeordnete Gehilfin des Mannes gestaltet. (Anhang III stellt die EDB-Verse der Lu-therübersetzung von 1545 gegenüber.) 4. Der Sündenfall wird als Rechtsbruch beschrieben, der den Wechsel von der Schöpfungsord-nung im Paradies zur Weltordnung auslöst, die mit den Urteilen Gottes über Frau und Mann beginnt (Genesis 3). Die Urteile fassen die Ehe in einem Diagonalkreuz, welches vier Faktoren untrennbar verbindet: Herrschaft mit Unterordnung sowie hilffen (Gebären) mit Tod. Die Ge-schlechterunterschiede sind konstituierend für die Ehe im Diagonalkreuz. In der EDB lassen sich drei Paarkonstellationen unterscheiden: die Ehe im Diagonalkreuz zwischen dem guten weib und dem weisen Mann, die Ehe ohne Diagonalkreuz zwischen dem un-weib und dem unweisen Mann und die nichteheliche Geschlechterbeziehung zwischen dem gemeinem weib und dem ee-brecher. Das zweite Kapitel der Dissertation vergleicht die alttestamentarischen Ehekonzepte der EDB mit denen der Dichtung Ackermann aus Böhmen. Die rhetorische Form des Streitgesprächs zwischen Witwer und hern Tot zeigt die Struktur eines deutschrechtlichen Prozesses. In diesem Rahmen gewinnen die gegensätzlichen Aussagen über die Ehe die Bedeutung von Rechtspositionen, die in konträren göttlichen Herrschaftsordnungen verortet werden. Die vom Witwer vertretene Herrschaftsordnung beruht auf der alttestamentarischen Rechtsordnung der EDB, während die Positionen des hern Tot diese Rechtsordnung verkehren, indem er die Herrschaftsordnung der Welt als sein Eigen definiert. Ein weiteres Ergebnis des Vergleichs zwischen der EDB und dem Ackermann aus Böhmen ist, dass sowohl die alttestamentarischen Bücher als auch die Dichtung Rechtsfiguren präsentieren. Entscheidend sind in beiden Texten die Urteile Gottes, die jeweils einen Paradigmenwechsel kon-stituieren. In der EDB wird nach dem Sündenfall die (paradiesische) Rechtsordnung in die Rechtsordnung ee gewandelt. Im Ackermann wird die alttestamentarische Rechtsordnung ee der EDB durch die ordenung Tod ersetzt, mit der zugleich die Ordnung Paar nicht mehr gilt. Die Urtei-le Gottes in der EDB definieren das Paar als zweigeschlechtlichen Menschen, das Urteil im Ackermann charakterisiert zwei Einzelmenschen: Mann oder Frau. Damit wird die zentrale Bedeutung der Ehefrau als hilffen zum Heil ihres Mannes aufgehoben, weil die wechselseitige Angewiesenheit von Mann und Frau nicht mehr gegeben ist. Insofern ist hier ein wichtiger Schritt zum reformatorischen Eheverständnis zu erkennen.

Distinct Unfolding and Refolding Pathways of Ribonuclease A Revealed by Heating and Cooling Temperature Jumps

Heating and cooling temperature jumps (T-jumps) were performed using a newly developed technique to trigger unfolding and refolding of wild-type ribonuclease A and a tryptophan-containing variant (Y115W). From the linear Arrhenius plots of the microscopic folding and unfolding rate constants, activation enthalpy (ΔH#), and activation entropy (ΔS#) were determined to characterize the kinetic transition states (TS) for the unfolding and refolding reactions. The single TS of the wild-type protein was split into three for the Y115W variant. Two of these transition states, TS1 and TS2, characterize a slow kinetic phase, and one, TS3, a fast phase. Heating T-jumps induced protein unfolding via TS2 and TS3; cooling T-jumps induced refolding via TS1 and TS3. The observed speed of the fast phase increased at lower temperature, due to a strongly negative ΔH# of the folding-rate constant. The results are consistent with a path-dependent protein folding/unfolding mechanism. TS1 and TS2 are likely to reflect X-Pro114 isomerization in the folded and unfolded protein, respectively, and TS3 the local conformational change of the β-hairpin comprising Trp115. A very fast protein folding/unfolding phase appears to precede both processes. The path dependence of the observed kinetics is suggestive of a rugged energy protein folding funne

Estabilitat conformacional de variants de la ribonucleasa A: pressió i temperatura com a inductors dels desplegament proteic

A fi d'analitzar la contribució de la regió C-terminal proposada com a iniciadora del plegament (CFIS 106-118) a l'estabilitat de l'RNasa A, els residus alifàtics d'aquesta regió es van substituir, mitjançant mutagènesi dirigida, per altres residus en els quals la cadena lateral alifàtica era rogressivament escurçada. La major part de les substitucions projectades suposaven delecions no disruptives de grups metil(è). A més, es va reemplaçar la Tyr115 per un Trp, de manera que, potencialment, s'introduïa una única sonda fluorescent, no desestabilitzant, per tal de seguir els canvis conformacionals que es poguessin generar en la regió durant el procés de legament/desplegament de la proteïna. Tant els paràmetres cinètics, com els espectres d'FTIR i CD, determinats per cadascuna de les ribonucleases variants, indiquen que els reemplaçaments aminoacídics efectuats presenten, en general, poc o cap efecte en l'estructura nativa i en l'activitat de l'enzim. Es va emprar l'espectroscòpia d'absorció a l'ultraviolat de quarta derivada, la fluorescència (per la variant amb Trp) i l'espectroscòpia d'infraroig per transformada de Fourier, per tal de seguir i caracteritzar, en condicions d'equilibri, les transicions conformacionals de cada variant en funció de la pressió i de la temperatura. Els resultats es van comparar amb els que es van obtenir per la proteïna salvatge. Per determinar més a fons les característiques del procés de desplegament de la variant Y115W, les transicions de desnaturalització induïdes per urea d'aquesta variant i de la proteïna salvatge, van ésser examinades per mitjà d'electroforesi en gradient d'urea i espectroscòpia de fluorescència. Curiosament, els canvis conformacionals que resulten de la desnaturalització per pressió són molt semblants als que s'obtenen per temperatura. Enfront d'un augment gradual tant de pressió com de temperatura, l'estructura terciària i els elements d'estructura secundària de les proteïnes estudiades es perden de manera conjunta i reversible. Aquestes variacions estructurals que es promouen descriuen un procés de desplegament molt cooperatiu i en dos estats. Atès que ambdues tècniques (UV i FTIR) utilitzen cadascuna un règim de concentració proteica molt diferent, els resultats indiquen que el procés de desplegament per pressió i per temperatura és intramolecular. Els resultats obtinguts suggereixen que la hidrofobicitat i el volum de les cadenes laterals del CFIS, juntament amb les interaccions de van der Waals entre elements d'estructura secundària intervenen de manera molt notable en l'estabilització de la proteïna. Entre els diferents aminoàcids alifàtics que pertanyen al CFIS C-terminal, la Val108 és el residu més important per tal de preservar la integritat estructural de l'estat natiu. Els reemplaçaments en aquesta posició causen petites alteracions conformacionals i una gran desestabilització de la proteïna (per exemple, el punt mig de la transició de desnaturalització per pressió i per temperatura de la variant V108G disminueix uns 592 MPa i 25ºC, respectivament, respecte a la proteïna salvatge). D'acord amb els resultats obtinguts, la variant Y115W ofereix una sonda útil per tal de seguir la cinètica de plegament/desplegament de l'RNasa A.

Estudi d'una metal·lotioneïna d'alzina surera (QsMT)

En aquest treball es caracteriza per primera vegada la capacitat de coordinació metàl·lica d'una metal·lotineïna (MT) de planta i es proposa un model de plegament per a les MTs de planta en general. Els resultat mostren que aquestes proteïnes poden tenir un paper molt important en la regulació de l'estat redox de les cèl·lules, probablement a través de la coordinació a Cu. Les MTs de planta són proteïnes molt desconegudes. Es postula que participen en l'homeòstasi del Cu i en la protecció contra l'estrès oxidatiu, però es desconeix la capacitat de coordinació metàl·lica i el plegament. En aquest treball s'han estudiat una metal·lotioneïna d'alzina surera, QsMT, aïllada d'una llibreria de cDNA de fel·lema. Els objectius concrets han estat: (1) estudiar l'expressió de QsMT i la resposta a l'estrès oxidatiu; (2) determinar la capacitat de coordinació metàl·lica i la funcionalitat in vivo; (3) fer una aproximació al plegament de les MTs de planta. L'expressió del gen s'ha estudiat mitjançant hibridació in situ en plàntules i en embrions d'alzina surera. QsMT s'expressa majoritàriament en cèl·lules amb fort estrès oxidatiu, associat a la síntesi de polifenols (suberització i lignificació) i a la senescència. També s'expressa en cèl·lules meristemàtiques, cèl·lules en divisió molt activa on la funció de les MTs podria estar relacionada amb el manteniment de l'estat redox. L'aplicació d'estrès oxidatiu exogen (H2O2 i paraquat) incrementa fortament l'expressió de QsMT en teixits amb expressió constitutiva, confirmant la regulació de l'expressió del gen per estrès oxidatiu. Per l'estudi de les propietats de coordinació metàl·lica es va expressar QsMT en cèl·lules d'E. coli en medi de cultiu suplementat amb Cu, Zn o Cd. Es van aïllar els agregats metàl·lics corresponents i es van analitzar mitjançant tècniques espectroscòpiques i espectromètriques (ICP-OES, ESI-MS i CD). Els resultats mostren que QsMT coordina de forma estable Cu (8 ions metàl·lics/molècula), Zn (4 ions de Zn/molècula) i Cd (6 ions de Cd/molècula), i adopta una estructura especialment quiral en coordinació a Cu. L'elevada capacitat quelant de la proteïna i la quiralitat de l'estructura indiquen que QsMT possiblement té preferència metàl·lica pel Cu i per tant una funció relacionada amb aquest metall in vivo. Estudis de complementació en llevat demostren que QsMT coordina Cu de forma funcional in vivo. En coordinació a Cd QsMT presenta una peculiaritat no observada fins ara en altres MTs: la participació d'ions sulfur en la formació de l'agregat metàl·lic incrementant la capacitat de coordinació metàl·lica (6 ions metàl·lics divalents de Cd enlloc de 4 ions de Zn). A més QsMT coordina Cd de forma funcional en llevat, i per tant la seva funció també podria estar relacionada amb la destoxicació de Cd en la planta. QsMT s'ha utilitzat com a model per fer una aproximació al plegament de les MTs de planta. Amb aquest objectiu vam dissenyar tres pèptids mutants derivats de QsMT: N25 corresponent a la zona rica en cisteïna en posició amino-terminal, C18 corresponent a la zona rica en cisteïna en posició carboxil-terminal, i N25-C18 corresponent a les dues zones riques en cisteïna enllaçades per 4 glicines substituint la zona central de 39 aminoàcids. Es van expressar i estudiar aquests pèptids per les mateixes tècniques utilitzades en l'estudi de QsMT. Els resultats indiquen que QsMT es plega formant un sol agregat metàl·lic per la interacció de les dues zones riques en cisteïna. En aquest model la zona central d'enllaç, típica de les MTs de planta, no participa en la coordinació metàl·lica però és imprescindible per a la funció de la proteïna. El paper de la zona central podria variar en funció del metall que coordina, participant en el plegament i estructura de la proteïna quan coordina Zn i Cd i en la seva regulació i estabilització quan coordina Cu.

Destierro y redención: el «síndrome de Adán y Eva» en La belleza del mundo de Héctor Tizón (Crítica)

En este ensayo, el autor plantea un diálogo entre la novela La belleza del mundo, de Héctor Tizón, y los arquetipos bíblicos de Adán y Eva, la pérdida del paraíso y el destierro, y el retorno al Edén. A partir de la traición primigenia de la esposa del protagonista, se inicia la integración a un tiempo cíclico e infinito –el del exilio. En el destierro, el protagonista está marcado por su afán de anular la temporalidad real y, a la vez, su propia identidad, intenta forzosamente olvidar la propia historia, lo cual lo conduce a una crisis de identidad. Al cabo de un largo recorrido, se plantea la necesidad de incorporar los acontecimientos de la vida a un tiempo mítico que regenere y perpetúe todas las acciones, y en el cual se busque el sufrimiento para alcanzar la salvación. El autor evidencia paralelismos diversos del texto con la doctrina cristiana: el protagonista comprende que para regresar a su propio centro debe perdonar. Y eso solo es posible regresando, enfrentando su pasado: el tiempo de redención es un regreso, pero el mismo-nuevo sitio no vuelve a ser jamás el paraíso.

Peptide mediated formation of hierarchically organized solution and solid state polymer nanostructures

Biologically-inspired peptide sequences have been explored as auxiliaries to mediate self-assembly of synthetic macromolecules into hierarchically organized solution and solid state nanostructures. Peptide sequences inspired by the coiled coil motif and "switch" peptides, which can adopt both amphiphilic alpha-helical and beta-strand conformations, were conjugated to poly(ethylene glycol) (PEG). The solution and solid state self-assembly of these materials was investigated using a variety of spectroscopic, scattering and microscopic techniques. These experiments revealed that the folding and organization properties of the peptide sequences are retained upon conjugation of PEG and that they provide the driving force for the formation of the different nanoscale structures which were observed. The possibility of using defined peptide sequences to direct structure formation of synthetic polymers together with the potential of peptide sequences to induce a specific biological response offers interesting prospects for the development of novel self-assembled and biologically active materials.