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Pyrimidines
Published in Mihai V. Putz, New Frontiers in Nanochemistry, 2020
Nicoleta A. Dudaş, Mihai V. Putz
The start of the prebiotic chemistry of nucleobases is considered to be HCN (Sponer, 2016). In the last decades, many experimental information has been accumulated about this molecule and the conversion from HCN to nucleotides is well characterized (Sponer, 2016). Nucleobases have been synthesized from simple precursor molecules, like HCN, urea or cyano-acetylene (Sponer, 2016). Formamide (NH2CHO), the hydrolysis product of HCN, an alternative to HCN, or a possible nonvolatile source of HCN is a thermodynamically more stable and less reactive variant, that it could accumulate on the surface of the early Earth (probably as the thermal dissociation product of ammonium-formate) (Figure 41.10) (Saladino, 2012b, 2013a,b). Formamide also have been observed in the comets, in the stellar objects, in the interstellar medium, in carbonaceous chondrites, as a common constituent of star-forming regions that foster planetary systems within the galactic habitable zone (Saladino, 2013a, 2015, 2016).
Acetyl-protected cytosine and guanine containing acrylics as supramolecular adhesives
Published in The Journal of Adhesion, 2019
Keren Zhang, Gregory B Fahs, Evan Margaretta, Amanda G Hudson, Robert B Moore, Timothy E. Long
Adenine, thymine, cytosine, and guanine comprise the primary nucleobases in deoxyribonucleic acid (DNA). The molecular recognition between purines and pyrimidines stabilizes the double helical structure of DNA and encodes genetic information for living organisms. This complementary hydrogen bonding between nucleobase pairs inspired many researchers to investigate and design nucleobase-containing supramolecular polymers with desirable self-assembled morphologies and physical properties.[10,22,35–45] Among the four primary nucleobases in DNA, earlier literature focuses on adenine and thymine derivatives due to their relatively straight-forward synthesis.[46] Long et al. previously designed novel adenine and thymine-containing acrylic copolymers as supramolecular adhesives.[9] In contrast, research on cytosine and guanine-containing polymers remains relatively unexplored due to multiple nucleophilic sites and challenging solubility of cytosine and guanine. However, the guanine-cytosine nucleobase pair affords a much stronger triple complementary interaction (~104 M−1 in CDCl3) compared to adenine-thymine (102 M−1 in CDCl3), and guanine and cytosine both form stronger self-associations compared to adenine and thymine.[47]
Biocompatible conjugation for biodegradable hydrogels as drug and cell scaffolds
Published in Cogent Engineering, 2020
Nucleobase functionalized biopolymers could assemble into biomaterials through specific nucleobase pairing (M. Fan, Zhang et al., 2015; Manna et al., 2009; Van de Manakker et al., 2009; Q. Wang et al., 2007). These successful results clearly illustrate that specific nucleobase pairing promise as scaffolding materials for cell cultures and tissue engineering. More recently, a biological hydrogel was self-assembled via the Watson-Crick base pairing of thymine- and adenine- functionalized star PEG (H. Tan, Xiao et al., 2012). This work should bring up a novel methodology to generate robust injectable scaffolds with tailorable properties for biomedical applications. The biological self-assembly PEG hydrogel system is established by the Watson-Crick base pairing between thymine (T) and adenine (A) via the hydrogen bonding (Figure 2a). Compared with linear PEG, multi-arm star-shaped PEG has the nature to induce stereo-complex formation, which shows promise in biomedically relevant hydrogel systems (M. Fan, Yan, Tan, Miao et al., 2014; H. Tan, Xiao et al., 2012). Firstly, thiol thymine (T-SH) and thiol adenine (A-SH) were synthesized, respectively. Maleimide terminated four-arm PEG (PEG-Mal) was functionalized with either T-SH or A-SH functionalities as self-assembly precursors via the Michael-type addition. After dissolution and a mixture of precursors in an aqueous environment, a stereo-PEG hydrogel network was self-assembled due to the formation of pairing complexes. Remarkably, incubation temperature has a significant influence on the swelling of this self-assembly PEG hydrogels (Figure 2b & c). Compared to the 20°C and 37°C, the swelling ratio of hydrogel significantly increased after 24 h incubation at 50°C. Insulin-loaded hydrogels caused a significant increase in ASCs proliferation in vitro after 7 days of incubation. The attached ASCs were present in the superficial area of the biological hydrogel and maintained their polygonal morphologies with size as ~20 μm (Figure 2d). Viable cells were observed after 7 day of culture, and more than 98% of the ASCs survived. Elliptical or round-shaped cells were uniformly distributed in the hydrogel (Figure 2e), which is an indicator of phenotype retention of ASCs and is essential for matrix formation. Spherical-shaped ASCs were distributed in the scaffold, indicative of the biological nature of the hydrogel for cell survival. These unique characteristics of this biological hydrogel make it a promising candidate as an injectable scaffold for pharmaceutical and biomedical applications.