Macrocyclic Tetramers—Structural Investigation of Peptide-Peptoid Hybrids

Outstanding affinity and specificity are the main characteristics of peptides, rendering them interesting compounds for basic and medicinal research. However, their biological applicability is limited due to fast proteolytic degradation. The use of mimetic peptoids overcomes this disadvantage, though they lack stereochemical information at the α-carbon. Hybrids composed of amino acids and peptoid monomers combine the unique properties of both parent classes. Rigidification of the backbone increases the affinity towards various targets. However, only little is known about the spatial structure of such constrained hybrids. The determination of the three-dimensional structure is a key step for the identification of new targets as well as the rational design of bioactive compounds. Herein, we report the synthesis and the structural elucidation of novel tetrameric macrocycles. Measurements were taken in solid and solution states with the help of X-ray scattering and NMR spectroscopy. The investigations made will help to find diverse applications for this new, promising compound class

Macrocyclic tetramers—structural investigation of peptide-peptoid hybrids

Outstanding affinity and specificity are the main characteristics of peptides, rendering them interesting compounds for basic and medicinal research. However, their biological applicability is limited due to fast proteolytic degradation. The use of mimetic peptoids overcomes this disadvantage, though they lack stereochemical information at the α-carbon. Hybrids composed of amino acids and peptoid monomers combine the unique properties of both parent classes. Rigidification of the backbone increases the affinity towards various targets. However, only little is known about the spatial structure of such constrained hybrids. The determination of the three-dimensional structure is a key step for the identification of new targets as well as the rational design of bioactive compounds. Herein, we report the synthesis and the structural elucidation of novel tetrameric macrocycles. Measurements were taken in solid and solution states with the help of X-ray scattering and NMR spectroscopy. The investigations made will help to find diverse applications for this new, promising compound class

Azide Thermolysis Frameworks: Self‐inflating, Porous, and Lightweight Materials

Porous organic materials have received increasing attention due to their potential applications, such as gas storage, gas separation, and catalysis. In this work, we present a series of aromatic, polyazide-containing building blocks that enable the formation of a new class of amorphous porous organic materials. The azide precursors are obtained in moderate to good yields following an easy synthesis procedure. By thermal decomposition, self-inflating porous structures named Azide Thermolysis Frameworks (ATFs) can be obtained. Modified thermogravimetric analysis is used to determine the onset temperature at which the azides decompose and the frameworks are formed. The frameworks are further investigated via infrared (IR) spectroscopy, elemental analysis, scanning electron microscopy (SEM), and gas adsorption measurements. Specific surface areas and pore sizes are determined by nitrogen adsorption measurements at 77 K using the Brunauer–Emmett–Teller method (BET) to give surface areas of up to 677 m$^2$/g for the ATF resulting from the thermolysis of TPB-Azide at 450 °C, which can compete with early Covalent Organic Frameworks (COFs). The specific surface area can be tuned by varying the thermolysis temperature

Biofunctionalization of Metal–Organic Framework Nanoparticles via Combined Nitroxide‐Mediated Polymerization and Nitroxide Exchange Reaction

Surface engineering of metal–organic framework nanoparticles (MOF NPs), and enabling their post-synthetic modulation that facilitates the formation of bio-interfaces has tremendous potential for diverse applications including therapeutics, imaging, biosensing, and drug-delivery systems. Despite the progress in MOF NPs synthesis, colloidal stability and homogeneous dispersity—a desirable property for biotechnological applications, stands as a critical obstacle and remains a challenging task. In this report, dynamic surfaces modification of MOF NPs with polyethylene glycol (PEG) polymer is described using grafting-from PEGylation by employing nitroxide-mediated polymerization (NMP) and inserting arginylglycylaspartic acid (RGD) peptides on the surface via a nitroxide exchange reaction (NER). The dynamic modification strategy enables tailoring PEG-grafted MOF NPs of the type UiO-66-NH2 with improved colloidal stability, and high dispersity, while the morphology and lattice crystallinity are strictly preserved. The interaction of PEG-grafted MOF NPs with human serum albumin (HSA) protein under physiological conditions is studied. The PEG-grafted colloidal MOF NPs adsorb less HSA protein than the uncoated ones. Therefore, the described approach increases the scope of bio-relevant applications of colloidal MOF NPs by reducing nonspecific interactions using NMP based PEGylation, while preserving the possibility to introduce targeting moieties via NER for specific interactions

Search for Alternative Two‐Step‐Absorption Photoinitiators for 3D Laser Nanoprinting

Recent studies have opened the door to a new generation of photoinitiators for 3D laser nanoprinting. Therein, the simultaneous absorption of two photons, commonly referred to as two-photon absorption, is replaced by the sequential absorption of two photons in two consecutive one-photon absorption processes. This process has been termed two-step absorption. Importantly, two-step absorption can be accomplished by inexpensive compact low-power continuous-wave blue laser diodes instead of femtosecond laser systems in the red spectral region. Red-shifting the second absorption step with respect to the first one results in an and-type optical nonlinearity based on two-color two-step absorption. Herein, alternatives are systematically explored to the few already reported one- and two-color two-step-absorption photoinitiators, including the search for photoinitiators that can be excited by one-color two-step absorption and be de-excited by a disparate laser color.</p

Biofunctionalization of Metal–Organic Framework Nanoparticles via Combined Nitroxide‐Mediated Polymerization and Nitroxide Exchange Reaction

Abstract Surface engineering of metal–organic framework nanoparticles (MOF NPs), and enabling their post‐synthetic modulation that facilitates the formation of bio‐interfaces has tremendous potential for diverse applications including therapeutics, imaging, biosensing, and drug‐delivery systems. Despite the progress in MOF NPs synthesis, colloidal stability and homogeneous dispersity—a desirable property for biotechnological applications, stands as a critical obstacle and remains a challenging task. In this report, dynamic surfaces modification of MOF NPs with polyethylene glycol (PEG) polymer is described using grafting‐from PEGylation by employing nitroxide‐mediated polymerization (NMP) and inserting arginylglycylaspartic acid (RGD) peptides on the surface via a nitroxide exchange reaction (NER). The dynamic modification strategy enables tailoring PEG‐grafted MOF NPs of the type UiO‐66‐NH2 with improved colloidal stability, and high dispersity, while the morphology and lattice crystallinity are strictly preserved. The interaction of PEG‐grafted MOF NPs with human serum albumin (HSA) protein under physiological conditions is studied. The PEG‐grafted colloidal MOF NPs adsorb less HSA protein than the uncoated ones. Therefore, the described approach increases the scope of bio‐relevant applications of colloidal MOF NPs by reducing nonspecific interactions using NMP based PEGylation, while preserving the possibility to introduce targeting moieties via NER for specific interactions

Polymers of Intrinsic Microporosity Containing [2.2]Paracyclophane Moieties : Synthesis and Gas Sorption Properties

The unique structure of [2.2]paracyclophane (PCP) with its rigidity, stability, and planar chirality has gained significant attention in polymer and material research. In this work, the incorporation of amino-functionalized PCPs within polymers of intrinsic microporosity (PIMs) is reported for the first time. Three different PCP-PIMs were prepared via a Tröger's base formation mechanism, and their structures characterized via solid-state NMR, MALDI-TOF, and SEM. Their porosity was evaluated using gas adsorption (N2 and CO2) based on theoretical calculations such as Brunauer–Emmett–Teller (BET), NLDFT pore size distribution (PSD) and ideal IAST CO2/N2 selectivity (15/85), a crucial separation when considering the capture of CO2 from flue gas. The surface areas were found to be between 200–230 m2 g−1 while the selectivity for CO2/N2 ranged from 46 to 70.Peer reviewe