Telechelic sequence-defined oligoamides: their step-economical synthesis, depolymerization and use in polymer networks

The application of sequence-defined macromolecules in material science remains largely unexplored due to their challenging, low yielding and time-consuming synthesis. This work first describes a step-economical method for synthesizing unnatural sequence-defined oligoamides through fluorenylmethyloxycarbonyl chemistry. The use of a monodisperse soluble support enables homogeneous reactions at elevated temperature (up to 65 °C), leading to rapid coupling times (<10 min) and improved synthesis protocols. Moreover, a one-pot procedure for the two involved iterative steps is demonstrated via an intermediate quenching step, eliminating the need for in-between purification. The protocol is optimized using γ-aminobutyric acid (GABA) as initial amino acid, and the unique ability of the resulting oligomers to depolymerize, with the formation of cyclic γ-butyrolactame, is evidenced. Furthermore, in order to demonstrate the versatility of the present protocol, a library of 17 unnatural amino acid monomers is synthesized, starting from the readily available GABA-derivative 4-amino-2-hydroxybutanoic acid, and then used to create multifunctional tetramers. Notably, the obtained tetramers show higher thermal stability than a similar thiolactone-based sequence-defined macromolecule, which enables its exploration within a material context. To that end, a bidirectional growth approach is proposed as a greener alternative that reduces the number of synthetic steps to obtain telechelic sequence-defined oligoamides. The latter are finally used as macromers for the preparation of polymer networks. We expect this strategy to pave the way for the further exploration of sequence-defined macromolecules in material science.

Sequence-defined antibody-recruiting macromolecules

Antibody-recruiting molecules represent a novel class of therapeutic agents that mediate the recruitment of endogenous antibodies to target cells, leading to their elimination by the immune system. Compared to single-ligand copies, macromolecular scaffolds presenting multiple copies of an antibody-binding ligand offer advantages in terms of increased complex avidity. In this study, we describe the synthesis of sequence-defined macromolecules designed for antibody recruitment, utilising dinitrophenol (DNP) as a model antibody-recruiting motif. The use of discrete macromolecules gives access to varying the spacing between DNP motifs while maintaining the same chain length. This characteristic enables the investigation of structure-dependent binding interactions with anti-DNP antibodies. Through solid-phase thiolactone chemistry, we synthesised a series of oligomers with precisely localised DNP motifs along the backbone and a terminal biotin motif for surface immobilisation. Utilising biolayer interferometry analysis, we observed that oligomers with adjacent DNP motifs exhibited enhanced avidity for anti-DNP antibodies. Molecular modelling provided insights into the structures and dynamics of the various macromolecules, shedding light on the accessibility of the ligands to the antibodies. Overall, our findings highlight that the use of sequence-defined macromolecules can contribute to our understanding of structure-activity relationships and provide insights for the design of novel antibody-recruiting therapeutic agents.

Reading Information Stored in Synthetic Macromolecules

The storage of information in synthetic (macro)molecules provides an attractive alternative for current archival storage media, and the advancements made within this area have prompted the investigation of such molecules for numerous other applications (e.g., anti-counterfeiting tags, steganography). While different strategies have been described for storing information at the molecular level, this Perspective aims to provide a critical overview of the most prominent approaches that can be utilized for retrieving the encoded information. The major part will focus on the sequence determination of synthetic macromolecules, wherein information is stored by the precise arrangement of constituting monomers, with an emphasis on chemically aided strategies, (tandem) mass spectrometry, and nanopore sensing. In addition, recent progress in utilizing (mixtures of) small molecules for information storage will be discussed. Finally, the closing remarks aim to highlight which strategy we believe is the most suitable for a series of specific applications, and will also touch upon the future research avenues that can be pursued for reading (macro)molecular information.

Phosphide in gallium bismuth: structural, electronic, elastic, and optical properties of GaPxBi1-x alloys

The structural, electronic, elastic, and optical properties of ternary alloys GaP_xBi_1-x as a function of phosphorus concentration were studied using ab initio calculations. We have used the full-potential linearized augmented plane wave method-based density functional theory. The potentials have been described by the generalized gradient and modified Becke-Johnson approximations. Results on lattice parameters, energy band gap, bulk modulus, elastic, and optical properties are reported. They are in good agreement with available theoretical and experimental data. Moreover, the dependence of structural and electronic properties on the composition has been analyzed. A deviation from linearity is observed for the lattice constant and the bulk modulus. In addition, the elastic constants and moduli were calculated and used to examine the mechanical stability. Both parts of dielectric-function and other optical parameters have been analyzed.

Uniform soluble support for the large-scale synthesis of sequence-defined macromolecules

A monodisperse soluble support is used as an effective tool for the large-scale, liquid-phase synthesis of sequence-defined macromolecules. This uniform support allows for direct characterisation and leads to a single peak in mass spectrometry.

Sequence-Encoded Macromolecules with Increased Data Storage Capacity through a Thiol-Epoxy Reaction

Sequence-encoded oligo(thioether urethane)s with two different coding monomers per backbone unit were prepared via a solid phase, two-step iterative protocol based on thiolactone chemistry. The first step of the synthetic cycle consists of the thiolactone ring opening with a primary amine, whereby the in situ released thiol is immediately reacted with an epoxide. In the second step, the thiolactone group is reinstalled to initiate the next cycle. This strategy allows to introduce two different coding monomers per synthetic cycle, rendering the resulting macromolecules especially attractive in the area of (macro)molecular data storage because of their increased data storage capacity. Subsequently, the efficiency of the herein reported synthesis route and the applicability of the dual-encoded sequence-defined macromolecules as a potential data storage platform have been demonstrated by unraveling the exact monomer order using tandem mass spectrometry techniques.

Applications of Discrete Synthetic Macromolecules in Life and Materials Science: Recent and Future Trends

In the last decade, the field of sequence-defined polymers and related ultraprecise, monodisperse synthetic macromolecules has grown exponentially. In the early stage, mainly articles or reviews dedicated to the development of synthetic routes toward their preparation have been published. Nowadays, those synthetic methodologies, combined with the elucidation of the structure-property relationships, allow envisioning many promising applications. Consequently, in the past 3 years, application-oriented papers based on discrete synthetic macromolecules emerged. Hence, material science applications such as macromolecular data storage and encryption, self-assembly of discrete structures and foldamers have been the object of many fascinating studies. Moreover, in the area of life sciences, such structures have also been the focus of numerous research studies. Here, it is aimed to highlight these recent applications and to give the reader a critical overview of the future trends in this area of research.

Sequence-defined oligoampholytes using hydrolytically stable vinyl sulfonamides: design and UCST behaviour

Water soluble sequence-defined oligoampholytes with precisely positioned charges were synthesised via an iterative solid-phase synthesis protocol using vinyl sulfonamide and acrylate building blocks.

From Sequence-Defined Macromolecules to Macromolecular Pin Codes

Dynamic sequence-defined oligomers carrying a chemically written pin code are obtained through a strategy combining multicomponent reactions with the thermoreversible addition of 1,2,4-triazoline-3,5-diones (TADs) to indole substrates. The precision oligomers are specifically designed to be encrypted upon heating as a result of the random reshuffling of the TAD-indole covalent bonds within the backbone, thereby resulting in the scrambling of the encoded information. The encrypted pin code can eventually be decrypted following a second heating step that enables the macromolecular pin code to be deciphered using 1D electrospray ionization-mass spectrometry (ESI-MS). The herein introduced concept of encryption/decryption represents a key advancement compared with current strategies that typically use uncontrolled degradation to erase and tandem mass spectrometry (MS/MS) to analyze, decipher, and read-out chemically encrypted information. Additionally, the synthesized macromolecules are coated onto a high-value polymer material, which demonstrates their potential application as coded product tags for anti-counterfeiting purposes.

Stereocontrolled, multi-functional sequence-defined oligomers through automated synthesis

In this work, stereocontrolled sequence-defined oligomers were prepared using an automated thiolactone-based platform that allows post-synthesis functionalisation.

Double-Modified Glycopolymers from Thiolactones to Modulate Lectin Selectivity and Affinity

Multivalent glycomaterials show high affinity toward lectins but are often nonselective as they lack the precise 3-D presentation found in native glycans. Here, thiolactone chemistry is exploited to enable the synthesis of glycopolymers with both a primary binding (galactose) and a variable secondary binding unit in close proximity to each other on the linker. These polymers are used to target the Cholera toxin B subunit, CTxB, inspired by its native branched glycan target, GM-1. The secondary, nonbinding unit was shown to dramatically modulate affinity and selectivity toward the Cholera toxin. These increasingly complex glycopolymers, assembled using accessible chemistry, can help breach the synthetic/biological divide to obtain future glycomimetics.

Precisely Alternating Functionalized Polyampholytes Prepared in a Single Pot from Sustainable Thiolactone Building Blocks

Polyampholytes with precisely alternating cationic and anionic functional groups were prepared using sustainable thiolactone building blocks in a simple one-pot procedure at room temperature and in water. Ring opening of the N-maleamic acid-functionalized homocysteine thiolactone monomer enabled the introduction of different functional groups into the polymer chain, which contributed to both ionic and hydrogen bonding interactions. The resulting polyampholytes exhibited various isoelectric points while maintaining high solubility in water under different pH and ionic strengths, which expands their potential applications. Finally, it is shown that the upper critical solution temperature (UCST) of these alternating polyampholytes in water/ethanol (30/70% vol) solutions can be tuned as a function of the content of ionic and hydroxyl groups.

Biomimetic artificial ion channels based on beta-cyclodextrin

Star polymers based on β-cyclodextrin were synthesized by a ''click-chemistry'' process and characterized by NMR, SEC and BLM. The resulting triazole functional groups create, at a specific pH range, electrostatic hindrance between pores inserted in lipid bilayers, preventing their aggregation, allowing formation of well-defined isolated unitary pores and mimicking biological natural channels.

Anionic ring-opening polymerization of ethylene oxide in DMF with cyclodextrin derivatives as new initiators

Anionic polymerization initiated by cyclodextrins suffers from a poor solubility of those derivatives in standard polymerization solvents. The possibility to perform ethylene oxide polymerization initiated by monofunctional initiators (allyl alcohol, 2-methoxyethanol) by living ring opening polymerization in DMF, a good solvent for any CD derivative, was demonstrated by SEC, (1)H and (13)C NMR analyses. The study was extended to the use of native CD as initiator, leading to the synthesis of ill-defined structures, explained by the reactivity scale of the various hydroxyl functions. Two selectively modified CD derivatives are then used to synthesize a new family of star-shaped poly(ethylene oxide) polymers with CD core, having 14 or 21 arms. The polymerization was found to be living and DOSY experiments confirmed the well-defined structures for the synthesized star-polymers.

Liquid-phase synthesis of block copolymers containing sequence-ordered segments

Monodisperse sequence-defined oligomers have been synthesized in solution in the absence of protecting groups. These structures have been prepared stepwise using two consecutive chemoselective reactions: 1,3-dipolar cycloaddition of terminal alkynes and azides and amidification of carboxylic acids with primary amines. These oligomers were efficiently constructed on either a conventional solid support (commercial Wang resin) or tailor-made soluble polystyrene supports synthesized by atom-transfer radical polymerization. The latter approach was found to be very versatile. Indeed, well-defined soluble macromolecular supports allowed not only the synthesis and cleavage of defined oligomers (i.e., sacrificial support) but also the preparation of noncleavable block copolymers containing sequence-defined segments.

Sequence control in polymer synthesis

The control over comonomer sequences is barely studied in macromolecular science nowadays. This is an astonishing situation, taking into account that sequence-defined polymers such as nucleic acids and proteins are key components of the living world. In fact, fascinating biological machines such as enzymes, transport proteins, cytochromes or sensory receptors would certainly not exist if evolution had not favored chemical pathways for controlling chirality and sequences. Thus, it seems obvious that synthetic polymers with controlled monomer sequences have an enormous role to play in the materials science of the next centuries. The goal of this tutorial review is to shed light on this highly important but embryonic field of research. Both biological and synthetic mechanisms for controlling sequences in polymerization processes are critically discussed herein. This state-of-the-art overview may serve as a source of inspiration for the development of new generations of synthetic macromolecules.

Per-O-(3-hydroxy)propyl-β-cyclodextrin: a cyclodextrin derivative bearing only primary hydroxyl groups

Natural beta-cyclodextrin (cyclomaltoheptaose) was treated with sodium hydride and allyl bromide to form the per-O-allyl-beta-cyclodextrin. 9-BBN, sodium hydroxide and hydrogen peroxide were then added to form, after adequate treatments, the desired per-O-(3-hydroxy)propyl-beta-cyclodextrin in yields close to 65%. This modified cyclodextrin, which bears only primary hydroxyl groups, can be used as a macro-initiator of the anionic polymerisation of ethylene oxide to form star-shaped polymers. The presence of only primary hydroxyl groups allows us to expect identical initiation kinetics for all the hydroxyl groups of the modified glucopyranosyl units.

Mortality in HIV-1-seropositive women, their spouses and their newly born children during 36 months of follow-up in Kinshasa, Zaïre

OBJECTIVE

To calculate 3-year mortality rates in HIV-1-seropositive and HIV-1-seronegative mothers, their newborn children and the fathers of these children.

DESIGN

Longitudinal cohort study of HIV-1-seropositive, age and parity-matched HIV-1-seronegative pregnant women, their newborn babies and the fathers of these children.

SETTING

Obstetric ward and follow-up clinic at a large municipal hospital in Kinshasa, Zaïre.

PARTICIPANTS

A total of 335 newborn children and their 327 HIV-1-seropositive mothers and 341 newborn children and their 337 HIV-1-seronegative mothers and the fathers of these children.

MAIN OUTCOME MEASURES

Rates of vertical HIV-1 transmission and maternal, paternal and early childhood mortality.

RESULTS

The lower and upper bounds of vertical transmission were 27 and 50%, respectively. The 3-year mortality rate was 44% in children with vertically acquired HIV-1 infection, 25% in children with HIV-1-seropositive mothers and indeterminant HIV-1 infection status, and 6% in uninfected children with HIV-1-seronegative mothers. HIV-1-seropositive women who transmitted HIV-1 infection to their most recently born child had lost a greater number of previously born children (mean, 1.5 versus 0.5; P < 0.05), were more likely to have had AIDS at delivery (25 versus 12%; P < 0.01) and were more likely to die during follow-up (22 versus 9%; P < 0.01) than HIV-1-seropositive women who did not transmit HIV-1 infection to their newborn child. Twenty-five out of 239 (10.4%) fathers of children with HIV-1-seropositive mothers, not lost to follow-up, died compared with three out of 310 (1%) fathers of children with HIV-1-seronegative mothers (P < 0.01).

CONCLUSIONS

Families in Kinshasa, Zaïre, in which the mother was HIV-1-seropositive experienced a five to 10-fold higher maternal, paternal and early childhood mortality rate than families in which the mother was HIV-1-seronegative.

Fertility rates in 238 HIV-1-seropositive women in Zaire followed for 3 years post-partum

Birth-control use and fertility rates were prospectively determined in 238 HIV-1-seropositive and 315 HIV-1-seronegative women in Kinshasa, Zaire, during the 36-month period following the delivery of their last live-born child. No women delivered children during the first follow-up year. Birth-control utilization rates (percentage use during total observation time) and fertility rates (annual number of live births per 1000 women of child-bearing age) in the second year of follow-up were 19% (107.4 per 1000) for HIV-1-seropositive women and 16% (144.7 per 1000) for HIV-1-seronegative women. In the third year of follow-up these rates were 26 (271.0 per 1000) and 16% (38.6 per 1000) for HIV-1-seropositive and HIV-1-seronegative women, respectively (P less than 0.05 for the difference in birth-control utilization and fertility rates between seropositive and seronegative women in the third year of follow-up). Seven (2.9%) of the 238 HIV-1-seropositive women initially included in the study brought their sex partners in for HIV-1 testing; three (43%) of these men were found to be HIV-1-seropositive. New HIV-1 infection did not have a dramatic effect on the fertility of seropositive women. The nearly uniform unwillingness of HIV-1-seropositive women to inform husbands or sexual partners of their HIV-1 serostatus accounted in large part for the disappointingly high fertility rates in seropositive women who had been provided with a comprehensive program of HIV counseling and birth control. Counseling services for seropositive women of child-bearing age which do not also include these women's sexual partners are unlikely to have an important impact on their high fertility rates.

A retrospective cohort study of the risk of tuberculosis among women of childbearing age with HIV infection in Zaire

To determine the risk of active tuberculosis associated with HIV infection, we retrospectively studied a cohort of HIV-seropositive and HIV-seronegative women participating in an HIV perinatal transmission study in Kinshasa, Zaire. After a median follow-up of 32 months, new cases of proven pulmonary or clinically diagnosed tuberculosis occurred in 19 of the 249 HIV-seropositive women (7.6%, 3.1 cases per 100 person-years) compared with 1 of the 310 HIV-seronegative women (0.3%, 0.12 cases per 100 person-years), for a relative risk of 26 (95% confidence interval, 5 to 125). Proven pulmonary tuberculosis was diagnosed in 7 HIV-seropositive women (2.8%, 1.2 cases per 100 person-years) and 1 HIV-seronegative woman (0.3%, 0.12 cases per 100 person-years), for a relative risk of 10 (95% confidence interval, 1.5 to 47). We estimated that 66 cases of proven pulmonary tuberculosis in 100,000 person-years of follow-up in women of childbearing age could be attributed to HIV; this is 35% of their estimated total incidence of proven pulmonary tuberculosis. Among those followed for 2 yr, 27 (11%) of 243 HIV-seropositive women died during 2 yr of follow-up compared with none of 296 HIV-seronegative women (p less than 0.001). In HIV-seropositive women with proven or clinically diagnosed tuberculosis mortality was even higher: 5 (26%) of the 19 HIV-seropositive women with proven pulmonary or clinically diagnosed tuberculosis died during follow-up compared with 22 (10%) of the 224 HIV-seropositive women not diagnosed as having tuberculosis (relative risk 2.7; 95% confidence interval, 1.1 to 6.3).(ABSTRACT TRUNCATED AT 250 WORDS)