The growing perspective of running out of crude oil followed by increasing prices for all crude oil-based materials, e.g., crude oil-based polymers, which have a huge number of practical applications but are usually neither biodegradable nor environmentally friendly, has resulted in searching for their substitutes—namely, bio-based polymers. Currently, both these types of polymers are used in practice worldwide. Owing to the advantages and disadvantages occurring among plastics with different origin, in this current review data on selected popular crude oil-based and bio-based polymers has been collected in order to compare their practical applications resulting from their composition, chemical structure, and related physical and chemical properties. The main goal is to compare polymers in pairs, which have the same or similar practical applications, regardless of different origin and composition. It has been proven that many crude oil-based polymers can be effectively replaced by bio-based polymers without significant loss of properties that ensure practical applications. Additionally, biopolymers have higher potential than crude oil-based polymers in many modern applications. It is concluded that the future of polymers will belong to bio-based rather than crude oil-based polymers.

Prohormone convertase (PC)1/3 is a eukaryotic serine protease in the subtilase family that participates in the proteolytic maturation of prohormone and neuropeptide precursors such as proinsulin and proopiomelanocortin. Despite the important role of this enzyme in peptide synthesis, how PC1/3 activity is regulated is still poorly understood. Using ion exchange chromatography and two-dimensional gel electrophoresis we found that natural PC1/3 present in AtT-20 cells and bovine chromaffin granules, as well as recombinant PC1/3 secreted from overexpressing Chinese hamster ovary cells, exists as multiple ionic forms. Gel filtration and cross-linking studies revealed that protein oligomerization and aggregation contribute greatly to variability in surface charge. The most acidic forms of PC1/3 contained both inactive aggregates as well as oligomerized 87-kDa PC1/3 that exhibited stable activity which was partially latent and could be revealed by dilution. No such latency was observed for the more basic, 66/74-kDa forms of PC1/3. Fractions containing these species were stabilized by preincubation with micromolar concentrations of either fluorogenic substrate or peptides containing pairs of basic residues. In addition, the most active form of 87-kDa PC1/3, a probable homodimer, was activated by preincubation with these same peptides. Cleavage by PC1/3 is often the initiating step in the biosynthetic pathway for peptide hormones, implying that this is a natural step for regulation. Our data suggest that enzyme oligomerization and peptide stabilization represent important contributing factors for the control of PC1/3 activity within secretory granules.

A modified method for the synthesis of 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra(benzoyl)methoxycalix(4)arene (1) and 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra(acetoyl)methoxycalix(4)arene (2) using 18-crown-6 as phase transfer catalyst is reported. Ligand 1 was structurally (¹H NMR and X-ray crystallography) and thermodynamically characterised. An account of the steps required for the formulation of an equation representative of the complexation process involving metal cations and macrocycles is given using as an illustrative example the interaction of 1 with the Na(I) cation. Thus, detailed thermodynamics of this system are first reported taking into account the solution properties of the reactants and the product in various solvents with the aim of assessing quantitatively the medium effect on the complexation process. The sodium:monoacetonitrile:1 complex was isolated and its molecular structure was determinated from X-ray diffraction data. The calix now adopts a more symmetric cone conformation than the free ligand and its hydrophobic cavity is filled with an acetonitrile solvent molecule. The hydrophilic pocket hosts the sodium cation which is in an eight-fold coordination with the four ethereal oxygen atoms [average d(Na–O) = 2.45(4) Å] and the four carbonyl oxygen atoms [average d(Na–O) = 2.51(4) Å] forming the corners of a distorted Archimedean square antiprism. The key structural features relevant to the complexation process are discussed. ¹H NMR and conductance measurements have been used to assess the interaction of 1 and 2 with alkali metal cations. Final conclusions are given. Attention is drawn about the relevance of detailed thermodynamic studies on cation complexation processes involving calixarene derivatives. This is discussed within the context of selectivity and the factors controlling it in solution processes.