Natural polymers such as sugars, proteins, and nucleic acids and synthetic polymers have deep structural and functional similarities, revealing a unified perspective that runs through chemistry and life.
Basic Knowledge
Correspondence between the three major natural polymers and synthetic polymers:
・Sugars (cellulose, starch): polymerization of monosaccharides through glycosidic bonds ↔ polyesters (ester bonds)
・Proteins: polymerization of amino acids through peptide bonds (amide bonds) ↔ nylon (also amide bonds)
・Nucleic acids (DNA, RNA): polymerization of nucleotides through phosphodiester bonds ↔ research on applications in DNA electronics
Functions of natural polymers:
・Enzymes (biocatalysts): substrate specificity, temperature and pH dependence, and regulatability
・Antibodies (immunity): antigen recognition; as medicines, monoclonal antibody drugs (rituximab, trastuzumab, Opdivo, etc., for cancer treatment)
・Receptors and channels: recognition of hormones and neurotransmitters; drug targets
Functionalization of synthetic polymers:
・Functional peptides: peptide drugs (insulin, GLP-1 analogs such as Ozempic)
・Nucleic acid drugs: antisense oligonucleotides, siRNA, and mRNA vaccines
・Polysaccharide drugs: heparin (anticoagulant), hyaluronic acid (joint injections and cosmetics)
・Biomaterials: collagen artificial skin, artificial blood vessels, and hydrogels
Sustainability and polymers:
・Bioplastics: PLA (polylactic acid, derived from corn), PHA (produced by microorganisms)
・Recycling: PET collection → recycled fibers → clothing (closed loop)
・Chemical recycling: technology that depolymerizes materials back to monomers (without material degradation)
・Microplastics: accumulation in the environment, biomagnification, and the challenge of reducing them
Correspondence between natural and synthetic polymers (proteins ⇔ nylon, sugars ⇔ polyesters)
Functional polymers (enzymes, antibodies, and receptors are natural functional materials)
Bioplastics (PLA, PHA, biodegradability)
Nucleic acid drugs and antibody drugs (new drug modalities of the 21st century)
Circular economy (a recycling and reuse-based circular society)
SDG 12 (responsible production and consumption; a guideline for the chemical industry)
Further Study (Principles and Applications)
The biopharmaceutical revolution of the 21st century: A paradigm shift from “small-molecule drugs (chemical synthesis)” used until the latter half of the 20th century to antibody drugs, nucleic acid drugs, cell therapy, and gene therapy. For example, cancer treatment includes:
・Small molecules (tyrosine kinase inhibitors such as imatinib)
・Antibodies (rituximab, Herceptin, Opdivo)
・CAR-T cell therapy (genetically modifying a patient’s own T cells)
・mRNA cancer vaccines (personalized, under development)
Synthetic biology: A method of programming cells. “Microbial factories” make bioplastics, biofuels, and pharmaceutical intermediates using microorganisms. Production of artemisinin (an antimalarial drug) by Amyris was an early success.
Green chemistry and polymers: Polymer synthesis from bio-based monomers such as succinic acid, lactic acid, and 1,4-butanediol is expanding in accordance with the 12 principles (atom economy, catalytic processes, renewable feedstocks, waste minimization, and so on). To achieve carbon neutrality by 2050 throughout the chemical industry, technologies that use CO2 as a feedstock (such as MOF catalysts), feedstock recycling of waste plastics, and electrification using renewable energy are essential.
- Natural and synthetic polymers are connected by the same “polymerization chemistry.”
- Proteins ⇔ nylon (both contain peptide/amide bonds)
- Sugars ⇔ polyesters (both contain ester/glycosidic bonds)
- 21st-century medicines are expanding to antibodies, nucleic acids, and cells.
- Bioplastics include PLA and PHA.
- A circular economy means recycling and regeneration.
- Synthetic biology enables microorganisms to manufacture useful products.
Points to Note (Common Confusions and Frequent Mistakes)
① Peptide bonds and amide bonds are the same (-CO-NH-). Proteins and nylon 66 are essentially based on the same chemistry. ② Do not forget that nucleic acids are polymers: a chain of base-sugar-phosphodiester bonds. ③ Biodegradability does not necessarily mean environmental degradability. PLA decomposes rapidly in composting facilities (high temperature and humidity), but it can remain in the ocean for several to several dozen years. ④ Differences between antibody drugs and small-molecule drugs: molecular mass (antibodies 150,000 Da vs. small molecules <500 Da), production method (cell culture vs. chemical synthesis), price (several million yen per year vs. tens of thousands to several tens of thousands of yen), and injection vs. oral administration.
Practice
- Describe the structural similarity and functional difference between the peptide bonds in proteins and the amide bonds in nylon 66.
- Give a representative example of a biodegradable plastic and its raw material, and describe its advantages and challenges compared with conventional plastics.
- Explain the characteristics of 21st-century drug modalities (antibodies, nucleic acids, and cells) compared with conventional small-molecule drugs.