Coarse-grained modeling and dynamics tracking of nanoparticles diffusion in human gut mucus.

The gastrointestinal (GI) tract's mucus layer serves as a critical barrier and a mediator in drug nanoparticle delivery. The mucus layer's diverse molecular structures and spatial complexity complicates the mechanistic study of the diffusion dynamics of particulate materials. In response, we developed a bi-component coarse-grained mucus model, specifically tailored for the colorectal cancer environment, that contained the two most abundant glycoproteins in GI mucus: Muc2 and Muc5AC. This model demonstrated the effects of molecular composition and concentration on mucus pore size, a key determinant in the permeability of nanoparticles. Using this computational model, we investigated the diffusion rate of polyethylene glycol (PEG) coated nanoparticles, a widely used muco-penetrating nanoparticle. We validated our model with experimentally characterized mucus pore sizes and the diffusional coefficients of PEG-coated nanoparticles in the mucus collected from cultured human colorectal goblet cells. Machine learning fingerprints were then employed to provide a mechanistic understanding of nanoparticle diffusional behavior. We found that larger nanoparticles tended to be trapped in mucus over longer durations but exhibited more ballistic diffusion over shorter time spans. Through these discoveries, our model provides a promising platform to study pharmacokinetics in the GI mucus layer.

Quantitative Study of Enantiomer-Specific State Transfer.

We here report on a quantitative study of enantiomer-specific state transfer, performed in a pulsed, supersonic molecular beam. The chiral molecule 1-indanol is cooled to low rotational temperatures (1-2 K) and a selected rotational level in the electronic and vibrational ground state of the most abundant conformer is depleted via optical pumping on the S_{1}←S_{0} transition. Further downstream, three consecutive microwave pulses with mutually perpendicular polarizations and with a well-defined duration and phase are applied. The population in the originally depleted rotational level is subsequently monitored via laser-induced fluorescence detection. This scheme enables a quantitative comparison of experiment and theory for the transfer efficiency in what is the simplest enantiomer-specific state transfer triangle for any chiral molecule, that is, the one involving the absolute ground state level, |J_{K_{a}K_{c}}⟩=|0_{00}⟩. Moreover, this scheme improves the enantiomer enrichment by over an order of magnitude compared to previous works. Starting with a racemic mixture, a straightforward extension of this scheme allows one to create a molecular beam with an enantiomer-pure rotational level, holding great prospects for future spectroscopic and scattering studies.

The Role of Polymer-AuNP Interaction in the Stimuli-Response Properties of PPA-AuNP Nanocomposites.

The helical sense control of dynamic helical polymers such as poly(phenylacetylene)s (PPAs) is greatly affected when they are conjugated to AuNPs through a strong thiol-Au connection, which restricts conformational changes at the polymer. Thus, the classical thiol-MNP bonds must be replaced by weaker ones, such as supramolecular amide-Au interactions. A straightforward preparation of the PPA-Au nanocomposite by reduction of a preformed PPA-Au3+ complex cannot be used due to a redox reaction between the two components of the complex which degrades the polymer. To avoid the interaction between the PPA and the Au3+ ions before the reduction takes place, the metal ions are added to the polymer solution capped as a TOAB complex, which keeps the PPA stable due to the lack of PPA-Au3+ interactions. Ulterior reduction of the Au3+ ions by NaBH4 affords the desired nanocomposite, where the AuNPs are stabilized by supramolecular anilide-AuNPs interactions. By using this approach, 3.7 nm gold nanoparticles are generated and aligned along the polymer chain with a regular distance between particles of 6 nm that corresponds to two helical pitches. These nanocomposites show stimuli-responsive properties and are also able to form macroscopically chiral nanospheres with tunable size.

Género, empoderamiento y complejidad: un conflicto de la mujer en el contexto de la modernidad / Gender, Empowerment, and Complexity: A Women's Conflict in the Context of Modernity

Resumen El rol femenino suele ser estereotipado, sin embargo, con el paso del tiempo la mujer ha adquirido progresivamente mayor empoderamiento y protagonismo en la sociedad, lo que ha permitido el desempeño de diversos roles al tiempo, tales como, estudiante, trabajadora, madre y cónyuge. El objetivo del estudio es identificar la percepción de mujeres frente a la multiplicidad de roles y su impacto social en la actualidad. Se realizó un estudio cualitativo, fenomenológico y hermenéutico, con una población de 19 estudiantes. Se aplicaron entrevistas semiestructurada sobre aspectos sociodemográficos y experiencias de las estudiantes en sus roles. La experiencia de sus roles fueron calificadas como duras, complejas, difíciles y le atribuyen significado de responsabilidad, compromiso, sacrificio. Se encontró que prevalecieron los sentimientos de dolor, tristeza y frustración. La sensación que más experimentan es la satisfacción y el empoderamiento; y percibieron muy escaso su tiempo. Las experiencias de las mujeres en el ejercicio de los roles, resultaron complejos y cargados de sentimientos encontrados y efectos históricamente marcados por el género, sin embargo, la satisfacción que genera en su crecimiento personal prevalece. No obstante, en el imaginario de las mujeres la repercusión social que esto genera recae en el descuido de la crianza de sus hijos.

Abstract The female role is usually stereotyped; however, over time, women have progressively acquired greater empowerment and prominence in society, which has allowed them to perform various roles at the same time: student, worker, mother, and spouse. This article aims to reveal women's perception of the multiplicity of roles and their current social impact. A qualitative, phenomenological, and hermeneutic study was carried out, with a population of 19 students. Semistructured interviews were conducted on sociodemographic aspects and experiences of the students in their roles. Their experience in the roles was qualified as hard, complex, and difficult, and they attribute it meanings of responsibility, commitment, and sacrifice. Feelings of pain, sadness, and frustration prevailed. The feelings they experienced the most were satisfaction and empowerment, and they perceived their time was scarce. Women's experiences in the exercise of their roles turned out to be complex, loaded with mixed feelings and effects historically marked by gender; however, the satisfaction it generates in their personal growth prevails. Nonetheless, in women's perspective, the social repercussion that this generates relies upon the neglect of their children's upbringing.

A guillotine amputation at the ankle level-how to quickly remove a septic foot: a case report.

As of 2014, diabetes is estimated to affect 422 million people globally. It is well recognised that lower extremity amputations secondary to diabetes have a high mortality rate perioperatively. The purpose of this article is to provide a simple, step-by-step guide to surgeons who need to perform a transtibial amputation. The case report of a 62-year-old female patient with poorly controlled diabetes who developed necrotising fasciitis of the lower extremity and systemic sepsis is used to illustrate the procedure. Knowing how to complete this operation is essential due to its effectiveness in quickly eliminating a source of pedal sepsis.

Biophysical determinants of biofilm formation in the gut.

The gastrointestinal (GI) tract harbors the most complex microbial ecosystem in the human body. The mucosal layer that covers the GI tract serves as a polymer-based defensive barrier that prevents the microbiome from reaching the epithelium and disseminating inside the body. Colonization of the mucus may result in the formation of structured polymicrobial communities or biofilms, a hallmark in pathologies such as colorectal cancer, inflammatory bowel disease, and chronic gut wounds. However, the mechanisms by which multispecies biofilms establish on the gut mucosa is unknown. Whether mucus-associated biofilms exist as part of a healthy mucosal barrier is still debated. Here, we discuss the impact that diet and microbial-derived polymers has on mucus structure and microcolony formation and highlight relevant biophysical forces that further shape nascent biofilms.

High-resolution UV spectroscopy of 1-indanol.

We report on rotationally resolved laser induced fluorescence (LIF) and vibrationally resolved resonance-enhanced multiphoton ionization (REMPI) spectroscopy of the chiral molecule 1-indanol. Spectra of the S1← S0 electronic transition are recorded in a jet-cooled, pulsed molecular beam. Using two time-delayed pulsed lasers, the lifetimes of the S1 state of the two most stable conformers, referred to as eq1 and ax2, have been determined. The S1← S0 origin bands of these conformers as well as the transition to a vibrationally excited level in the S1 state of eq1 are recorded with full rotational resolution (25 MHz observed linewidth) by measuring the LIF intensity following excitation with a tuneable, narrowband cw laser. On selected rotationally resolved electronic transitions, Lamb-dips are measured to confirm the Lorentzian lifetime-contribution to the observed lineshapes. The rotationally resolved S1← S0 origin band of a neon-complex of eq1 is measured via LIF as well. The fit of the rotationally resolved LIF spectra of the origin bands to those of an asymmetric rotor yields a standard deviation of about 6 MHz. The resulting spectroscopic parameters are tabulated and compared to the outcome of ab initio calculations. For both conformers as well as for the Ne-eq1 complex, the geometric structures in the S0 and S1 states are discussed. For all systems, the transition dipole moment is mainly along the a-axis, the contributions along the b- and c-axes being about one order of magnitude smaller.

Implementing Zn2+ ion and pH-value control into artificial mussel glue proteins by abstracting a His-rich domain from preCollagen.

A His-rich domain of preCollagen-D found in byssal threads is derivatized with Cys and Dopa flanks to allow for mussel-inspired polymerization. Artificial mussel glue proteins are accessed that combine cysteinyldopa for adhesion with sequences for pH or Zn2+ induced ß-sheet formation. The artificial constructs show strong adsorption to Al2O3, the resulting coatings tolerate hypersaline conditions and cohesion is improved by activating the ß-sheet formation, that enhances E-modulus up to 60%.

Escherichia coli Adhesion and Biofilm Formation on Polydimethylsiloxane are Independent of Substrate Stiffness.

Bacterial adhesion and biofilm formation on the surface of biomedical devices are detrimental processes that compromise patient safety and material functionality. Several physicochemical factors are involved in biofilm growth, including the surface properties. Among these, material stiffness has recently been suggested to influence microbial adhesion and biofilm growth in a variety of polymers and hydrogels. However, no clear consensus exists about the role of material stiffness in biofilm initiation and whether very compliant substrates are deleterious to bacterial cell adhesion. Here, by systematically tuning substrate topography and stiffness while keeping the surface free energy of polydimethylsiloxane substrates constant, we show that topographical patterns at the micron and submicron scale impart unique properties to the surface which are independent of the material stiffness. The current work provides a better understanding of the role of material stiffness in bacterial physiology and may constitute a cost-effective and simple strategy to reduce bacterial attachment and biofilm growth even in very compliant and hydrophobic polymers.

Information-Based Design of Polymeric Drug Formulation Additives.

Tailor-made copolymers are designed based on a peptide-poly(ethylene glycol) (QFFLFFQ-PEG) conjugate as a blueprint, to solubilize the photosensitizer meta-tetra(hydroxyphenyl)chlorin (m-THPC). The relevant functionalities of the parent peptide-PEG are mimicked by employing monomer pairs that copolymerize in a strictly alternating manner. While styrene (S) or 4-vinylbenzyl-phthalimide (VBP) provide aromatic moieties like Phe, the aliphatic isobutyl side chain of Leu4 is mimicked by maleic anhydride (MA) that reacts after polymerization with isobutylamine to give the isobutylamide-carboxyl functional unit (iBuMA). A set of copolymer-PEG solubilizers is synthesized by controlled radical polymerization, systematically altering the length of the functional segment (DPn = 2, 4, 6) and the side chain functionalization (iBuMA, iPrMA, MeMA). The m-THPC hosting and release properties of P[S-alt-iBuMA]6-PEG reached higher payload capacities and more favored release rates than the parent peptide-PEG conjugate. Interestingly, P[S-alt-RMA]n-PEG mimics the sensitivity of the peptide-PEG solubilizer well, where the exchange of Leu4 residue by Val and Ala significantly reduces the drug loading by 92%. A similar trend is found with P[S-alt-RMA]n-PEG as the exchange of iBu → iPr → Me reduces the payload capacity up to 78%.

Calidad de vida en personas portadoras de ostomías digestivas / Quality of life in people with digestive ostomies

INTRODUCCIÓN: La realización de una ostomía digestiva ha de ocasionar en las personas alteraciones en las dimensiones del ser como físicas, mentales, sociales y culturales lo que genera compromisos en la calidad de vida. OBJETIVO: Evaluar el impacto que se presenta en la calidad de vida de la persona en condición de ostomizadas en la ciudad de Manizales. METODOLOGÍA: estudio desarrollado a través de una fase cuantitativa con diseño observacional descriptivo utilizando el cuestionario Montreaux para la valoración de la calidad de vida y una fase cualitativa, fenomenológica realizada por medio de entrevistas semiestructruadas en el que participaron 16 personas en condicion de ostomizados. RESULTADOS: Promedio de edad 56 años, El 75% de ellos pertenecia a estrato socioeconómico bajo, el 50% tenia con estudios de primaria y el 50% con estudios de secundaria. El 75% pertenecía al régimen de salud contributivo. Los resultados cuantitativos mostraron un índice de calidad de vida del 44,5%; el aspecto con porcentaje mas alto en la calidad de vida fue el hecho de no tener preocupaciones sociales 73%, por el contrario, el porcentaje más bajo se obtuvo en el aspecto relacionado con la actividad sexual 25%. Se identificó un porcentaje de autosuficiencia del 80%, pero una adaptación negativa en el 50% de los casos. Los resultados cualitativos, evidenciaron siete categorías que describen los aspectos que alteran la calidad de vida y el autocuidado: sentimiento de discapacidad, pérdida laboral, alteración de la imagen corporal, afrontamiento según duración y posición de la ostomía, proyección del futuro, aislamiento social y alteración de la sexualidad. CONCLUSIÓN: el índice de calidad de vida fue bajo y las categorías encontradas confirman los aspectos de la vida diaria de las personas en condición de ostomizados y la necesidad de brindar un cuidado integral donde el rol de enfermería este visible ampliamente.

INTRODUCTION. The performance of a digestive ostomy must cause alterations in the dimensions of the being such as physical, mental, social and cultural, which generates compromisesin the quality of life. OBJECTIVE. To evaluate the impact on the quality of life of the person with an ostomy condition in the city of Manizales. METHODOLOGY. Study developed through a quantitative phase with a descriptive observational design using the Montreaux questionnaire for the assessment of quality of life and a qualitative, phenomenological phase carried out through semi-structured interviews in which 16 people with ostomized conditions participated. RESULTS. Average age 56 years, 75% of them belonged to low socioeconomic status, 50% had primary education and 50% had secondary education. 75% belonged to the contributory health scheme. The quantitative results showed a quality of life index of 44.5%; The aspect with the highest percentage in quality of life was the fact of not having social concerns, 73%, on the contrary, the lowest percentage was obtained in the aspect related to sexual activity, 25%. A self-sufficiency percentage of 80% was identified, but a negative adaptation in 50% of the cases. The qualitative results showed seven categories that describe the aspects that alter the quality of life and self-care: feeling of disability, job loss, alteration of body image, coping according to duration and position of the ostomy, projection of the future, social isolation and alteration of sexuality. CONCLUSIONS. The quality of life index was low and the categories found confirm the aspects of daily life of people with an ostomy condition and the need to provide comprehensive care where the role of nursing is widely visible.

Toward Artificial Mussel-Glue Proteins: Differentiating Sequence Modules for Adhesion and Switchable Cohesion.

Artificial mussel-glue proteins with pH-triggered cohesion control were synthesized by extending the tyrosinase activated polymerization of peptides to sequences with specific modules for cohesion control. The high propensity of these sequence sections to adopt ß-sheets is suppressed by switch defects. This allows enzymatic activation and polymerization to proceed undisturbed. The ß-sheet formation is regained after polymerization by changing the pH from 5.5 to 6.8, thereby triggering O→N acyl transfer rearrangements that activate the cohesion mechanism. The resulting artificial mussel glue proteins exhibit rapid adsorption on alumina surfaces. The coatings resist harsh hypersaline conditions, and reach remarkable adhesive energies of 2.64 mJ m-2 on silica at pH 6.8. In in situ switch experiments, the minor pH change increases the adhesive properties of a coating by 300 % and nanoindentation confirms the cohesion mechanism to improve bulk stiffness by around 200 %.

Chiral gold-PPA nanocomposites with tunable helical sense and morphology.

A novel type of stimuli-responsive dynamic helical polymer-metal nanoparticle nanocomposite formed by a helical poly(phenylacetylene) (PPA) combined with gold nanoparticles (AuNPs) is described. Thus, several PPA copolymers containing the ethynyl-4-benzamide of (S)-phenylglycine methyl ester (M1) to dictate the helical structure/sense of the copolymer, and the ethynyl-4-benzamide of the 11-((2-(2-(2-aminoethoxy)ethoxy)ethyl)amino)undecane-1-thiol (M2) to link the copolymer to the AuNPs are prepared. Different morphologies of these nanocomposites were obtained by considering the thiol ratio and the self-assembly properties of the PPA, which generates from dispersed AuNPs to fibre-like structures. All these nanocomposites show a dynamic chiral behaviour, it being possible to manipulate their helical sense by the action of external stimuli. Moreover, it is possible to control the aggregation of these nanocomposites into macroscopically chiral nanospheres with low polydispersity by using Ba2+ as a crosslinking agent.

Bacterial Envelope Damage Inflicted by Bioinspired Nanostructures Grown in a Hydrogel.

Surface-associated bacterial communities, known as biofilms, are responsible for a broad spectrum of infections in humans. Recent studies have indicated that surfaces containing nanoscale protrusions, like those in dragonfly wings, create a hostile niche for bacterial colonization and biofilm growth. This functionality has been mimicked on metals and semiconductors by creating nanopillars and other high aspect ratio nanostructures at the interface of these materials. However, bactericidal topographies have not been reported on clinically relevant hydrogels and highly compliant polymers, mostly because of the complexity of fabricating nanopatterns in hydrogels with precise control of the size that can also resist aqueous immersion. Here, we report the fabrication of bioinspired bactericidal nanostructures in bacterial cellulose (BC) hydrogels using low-energy ion beam irradiation. By challenging the currently accepted view, we show that the nanostructures grown in BC affect preferentially stiff membranes like those of the Gram-positive bacteria Bacillus subtilis in a time-dependent manner and, to a lesser extent, the more deformable and softer membrane of Escherichia coli. Moreover, the nanostructures in BC did not affect the viability of murine preosteoblasts. Using single-cell analysis, we demonstrate that indeed B. subtilis requires less force than E. coli to be penetrated by nanoprobes with dimensions comparable to those of the nanostructured BC, providing the first direct experimental evidence validating a mechanical model of membrane rupture via a tension-induced mechanism within the activation energy theory. Our findings bridge the gap between mechano-bactericidal surfaces and low-dimensional materials, including single-walled carbon nanotubes and graphene nanosheets, in which a higher bactericidal activity toward Gram-positive bacteria has been extensively reported. Our results also demonstrate the ability to confer bactericidal properties to a hydrogel by only altering its topography at the nanoscale and contribute to a better understanding of the bacterial mechanobiology, which is fundamental for the rational design bactericidal topographies.

Chiral Conflict as a Method to Create Stimuli-Responsive Materials Based on Dynamic Helical Polymers.

A new multi-sensor material based on helical copolymers showing the chiral conflict effect have been prepared. It can successfully detect and identify diverse metal cations in solution. The design of this material has taken into account not only the opposite helical senses induced by the two chiral monomers in the copolymer, but also their dynamic behavior. The induced helical sense can thus be enhanced, diminished, or inverted by interaction with different stimuli (that is, metal ions). Thus, depending on both the copolymer compositions (such as monomer ratios and absolute configurations) and the nature of the metal ion, the response of these dynamic helical copolymers to adopt a single-handed P or M helix is unique, making it possible not only to detect their presence, but also to identify them individually. New multi-sensors materials based and inspired on this effect should arise in the future choosing appropriate monomers and stimuli.

Designing Nanostructured Ti6Al4V Bioactive Interfaces with Directed Irradiation Synthesis toward Cell Stimulation to Promote Host-Tissue-Implant Integration.

A new generation of biomaterials are evolving from being biologically inert toward bioactive surfaces, which can further interact with biological components at the nanoscale. Here, we present directed irradiation synthesis (DIS) as a novel technology to selectively apply plasma ions to bombard any type of biomaterial and tailor the nanofeatures needed for in vitro growth stimulation. In this work, we demonstrate for the first time, the influence of physiochemical cues (e.g., self-organized topography at nanoscale) of medical grade Ti6Al4V results in control of cell shape, adhesion, and proliferation of human aortic smooth muscle stem cells. The control of surface nanostructures was found to be correlated to ion-beam incidence angle linked to a surface diffusive regime during irradiation synthesis with argon ions at energies below 1 keV and a fluence of 2.5 × 1017 cm-2. Cell viability and cytoskeleton morphology were evaluated at 24 h, observing an advance cell attachment state on post-DIS surfaces. These modified surfaces showed 84% of cell biocompatibility and an increase in cytoplasmatic protusions ensuring a higher cell adhesion state. Filopodia density was promoted by a 3-fold change for oblique incidence angle DIS treatment compared to controls (e.g., no patterning) and lamellipodia structures were increased more than a factor of 2, which are indicators of cell attachment stimulation due to DIS modification. In addition, the morphology of the nanofeatures were tailored, with high fidelity control of the main DIS parameters that control diffusive and erosive regimes of self-organization. We have correlated the morphology and the influence in cell behavior, where nanoripple formation is the most active morphology for cell stimulation.

Balancing biofunctional and biomechanical properties using porous titanium reinforced by carbon nanotubes.

Despite the well-known advantages of the titanium-based implant systems, they still lack an optimal balance between biofunctionality and mechanical strength, especially regarding the modulation of cellular response and a desired implant osseointegration. In this work, we fabricated a nanocomposite based on porous commercially pure grade 4 titanium (c.p. Ti) reinforced with carbon nanotubes (CNT) at 5% and 10% w/w, with the aim of obtaining a nanocomposite with lower stiffness compared to traditional titanium-based implants and with the mechanical strength and bioactivity owed by the CNT. Results obtained by scanning electron microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy characterization showed that the CNT dispersed and incorporated into the porous c.p. Ti matrix. Interestingly, CNT were associated with a higher twining within neighbor Ti grains, which was indeed consistent with an increased in nano-hardness. Biological evaluation by MTT and Comet assay revealed that the nanocomposites did not induce genotoxicity and cytotoxicity on two different cells lines despite the presence of nickel at the surface. Accordingly, a purification step would be required before these CNT can be used for biomedical applications. Our results indicate that incorporation of CNT into porous c.p. Ti is a promising avenue to achieve an adequate balance between biofunctionality and mechanical strength in Ti-based scaffolds for tissue replacement. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 719-731, 2019.

Magnetic targeting of smooth muscle cells in vitro using a magnetic bacterial cellulose to improve cell retention in tissue-engineering vascular grafts.

Tissue-engineered vascular grafts (TEVG) use biologically-active cells with or without supporting scaffolds to achieve tissue remodeling and regrowth of injured blood vessels. However, this process may take several weeks because the high hemodynamic shear stress at the damaged site causes cellular denudation and impairs tissue regrowth. We hypothesize that a material with magnetic properties can provide the force required to speed up re-endothelization at the vascular defect by facilitating high cell density coverage, especially during the first 24 h after implantation. To test our hypothesis, we designed a magnetic bacterial cellulose (MBC) to locally target cells in vitro under a pulsatile fluid flow (0.514 dynes cm-2). This strategy can potentially increase cell homing at TEVG, without the need of blood cessation. The MBC was synthesized by an in situ precipitation method of Fe3+ and Fe2+ iron salts into bacterial cellulose (BC) pellicles to form Fe3O4 nanoparticles along the BC's fibrils, followed by the application of dextran coating to protect the embedded nanoparticles from oxidation. The iron salt concentration used in the synthesis of the MBC was tuned to balance the magnetic properties and cytocompatibility of the magnetic hydrogel. Our results showed a satisfactory MBC magnetization of up to 10 emu/g, which is above the value considered relevant for tissue engineering applications (0.05 emu/g). The MBC captured magnetically-functionalized cells under dynamic flow conditions in vitro. MBC magnetic properties and cytocompatibility indicated a dependence on the initial iron oxide nanoparticle concentration. STATEMENT OF SIGNIFICANCE: Magnetic hydrogels represent a new class of functional materials with great potential in TVEG because they offer a platform to (1) release drugs on demand, (2) speed up tissue regrowth, and (3) provide mechanical cues to cells by its deformability capabilities. Here, we showed that a magnetic hydrogel, the MBC, was able to capture and retain magnetically-functionalized smooth muscle cells under pulsatile flow conditions in vitro. A magnetic hydrogel with this feature can be used to obtain high-density cell coverage on sites that are aggressive for cell survival such as the luminal face of vascular grafts, whereas simultaneously can support the formation of a biologically-active cell layer that protects the material from restenosis and inflammation.

Chiral Coalition in Helical Sense Enhancement of Copolymers: The Role of the Absolute Configuration of Comonomers.

Both the role of the absolute configuration and the tendency of a chiral monomer to promote a certain helical scaffold in a poly(phenylacetylene) (PPA) have been evaluated to study the communication between two chiral monomers within a copolymer chain. Nineteen different PPA copolymer series-47 helical copolymers altogether-were prepared to explore the existence of a chiral-to-chiral communication mechanism. From the data obtained, we found that communication between two different chiral monomers emerges when both exhibit two special features: (a) a different conformational composition-one must exist in a single low-energy conformation ("chiral Sergeant") and the other must present two conformers ("chiral Soldier")-and (b) the induction of a similar scaffold in the PPA, either cis-cisoidal or cis-transoidal. In the selected systems, the chiral Soldier includes the 4-ethynylanilide (para position) of either (R)- or (S)-2-methoxy-2-phenylacetic acid pendants characterized by their conformational flexibility (equilibrium between synperiplanar and antiperiplanar conformations). The chiral Sergeant contains the same chiral groups but linked to the backbone in meta position [3-ethynylanilide of (R)- or (S)-2-methoxy-2-phenylacetic acid] and is selected on the basis of its restricted antiperiplanar conformation. Incorporation of a very small amount (1%) of the Sergeant into a chain composed of just the Soldier transforms the originally axially racemic chain into a helix with strong sense preference (either M or P) that is determined by the absolute configuration of the Soldier.

The role of the secondary structure of helical poly(phenylacetylene)s in the formation of nanoparticles from polymer-metal complexes (HPMCs).

The great importance of the secondary structure (compressed/stretched) of helical poly(phenylacetylene)s (PPAs) in the formation of nanostructures (nanospheres and nanotoroids) by complexation with metal ions of diverse valences is demonstrated. PPAs bearing the same chelating units [anilide of (R)-methoxyphenylacetic acid] but displaying different helical scaffolds show great differences in their nanostructuration due to the different secondary structures of their helices despite the analogous ways in which their mono- and divalent metal ions form complexes. This key 3-D structural feature has not been taken into account previously when studying the nanostructuration of helical polymer-metal complexes (HPMCs).