Temperature acclimation in the crayfish: Effects on phospholipid fatty acids

Acclimation to different temperatures by a poikilothermous animal must include modification of its membrane lipids to maintain the proper physical properties. The simplest way to achieve this acclimation would seem to be by modification of the phospholipid fatty acids. In a freshwater cray-fish,Procambarus clarkii, rapid changes in the degree of unsaturation of newly synthesized phospholipid fatty acids were correlated with changes in environmental temperature, both in whole animals and in slices of hepatopancreas tissue. At 5 C, the rate of fatty acid synthesis was about half that occurring at 23 C. Hepatopancreas tissue from animals acclimated to either 5 C or 23 C, when incubated for 2 hr at 5 C, incorporated a higher percentage of exogenous [1-¹⁴C] acetate into polyunsaturated acids (27–38% of the radioactivity in total fatty acids) than when incubated at 23 C (12–14%); conversely, more saturated fatty acids were synthesized at 23 C (73–80% vs 51–73%). The higher average unsaturation of the fatty acids biosynthesized at 5 C constitutes an effective response to the animal's need for modification of lipids to maintain adequate membrane function at the lower environmental temperature. Presented at the AOCS meeting in Mexico City, Mexico, April 27–May 2, 1974. Work done at the Laboratory of Nuclear Medicine and Radiation Biology, University of California, Los Angeles, CA 90024.     

Engineering Field Effect Transistors with 2D Semiconducting Channels: Status and Prospects

The continuous miniaturization of field effect transistors (FETs) dictated by Moore's law has enabled continuous enhancement of their performance during the last four decades, allowing the fabrication of more powerful electronic products (e.g., computers and phones). However, as the size of FETs currently approaches interatomic distances, a general performance stagnation is expected, and new strategies to continue the performance enhancement trend are being thoroughly investigated. Among them, the use of 2D semiconducting materials as channels in FETs has raised a lot of interest in both academia and industry. However, after 15 years of intense research on 2D materials, there remain important limitations preventing their integration in solid‐state microelectronic devices. In this work, the main methods developed to fabricate FETs with 2D semiconducting channels are presented, and their scalability and compatibility with the requirements imposed by the semiconductor industry are discussed. The key factors that determine the performance of FETs with 2D semiconducting channels are carefully analyzed, and some recommendations to engineer them are proposed. This report presents a pathway for the integration of 2D semiconducting materials in FETs, and therefore, it may become a useful guide for materials scientists and engineers working in this field.     

Molecular Mechanisms of Taste Recognition: Considerations about the Role of Saliva

The gustatory system plays a critical role in determining food preferences and food intake, in addition to nutritive, energy and electrolyte balance. Fine tuning of the gustatory system is also crucial in this respect. The exact mechanisms that fine tune taste sensitivity are as of yet poorly defined, but it is clear that various effects of saliva on taste recognition are also involved. Specifically those metabolic polypeptides present in the saliva that were classically considered to be gut and appetite hormones (i.e., leptin, ghrelin, insulin, neuropeptide Y, peptide YY) were considered to play a pivotal role. Besides these, data clearly indicate the major role of several other salivary proteins, such as salivary carbonic anhydrase (gustin), proline-rich proteins, cystatins, alpha-amylases, histatins, salivary albumin and mucins. Other proteins like glucagon-like peptide-1, salivary immunoglobulin-A, zinc-α-2-glycoprotein, salivary lactoperoxidase, salivary prolactin-inducible protein and salivary molecular chaperone HSP70/HSPAs were also expected to play an important role. Furthermore, factors including salivary flow rate, buffer capacity and ionic composition of saliva should also be considered. In this paper, the current state of research related to the above and the overall emerging field of taste-related salivary research alongside basic principles of taste perception is reviewed.     

Random and block copolymers based on 4-methyl-1-pentene and 1-pentene

The zirconium acetamidinate catalyst {Cp*Zr(Me)₂[N(Et)C(Me)N(tBu)]} (Cp* = ?⁵-C₅Me₅) was used to synthesize both random and block copolymers based on 4-methyl-1-pentene (4M1P) and 1-pentene. The polymers have been characterized by NMR spectroscopy, SEC, DSC, high temperature HPLC and CRYSTAF. Unexpectedly, the yields and molecular weights decreased with increasing amounts of 1-pentene. The reason for this behavior is that 1-pentene occasionally undergoes 2,1-misinsertions trapping the catalyst in a dormant state. These 2,1-misinsertions do not seem to occur with the bulky 4M1P (branched α-olefin). Adding a small amount of ethylene reactivates the catalyst. Unlike most semi-crystalline polymers, the density of the crystalline phase of isotactic P4M1P can be lower than of the amorphous phase, when crystallized under very high pressures. To characterize this peculiar behavior of 4M1P-based polymers, various samples have been subjected to Pressure-Volume-Temperature (PVT) measurements. While the P4M1P homopolymers and block copolymers show the expected decrease in specific volume upon crystallization, the 4M1P-rich random copolymers proved not to vary in specific volume under the same conditions.     

Salivary defense proteins: their network and role in innate and acquired oral immunity

There are numerous defense proteins present in the saliva. Although some of these molecules are present in rather low concentrations, their effects are additive and/or synergistic, resulting in an efficient molecular defense network of the oral cavity. Moreover, local concentrations of these proteins near the mucosal surfaces (mucosal transudate), periodontal sulcus (gingival crevicular fluid) and oral wounds and ulcers (transudate) may be much greater, and in many cases reinforced by immune and/or inflammatory reactions of the oral mucosa. Some defense proteins, like salivary immunoglobulins and salivary chaperokine HSP70/HSPAs (70 kDa heat shock proteins), are involved in both innate and acquired immunity. Cationic peptides and other defense proteins like lysozyme, bactericidal/permeability increasing protein (BPI), BPI-like proteins, PLUNC (palate lung and nasal epithelial clone) proteins, salivary amylase, cystatins, prolin-rich proteins, mucins, peroxidases, statherin and others are primarily responsible for innate immunity. In this paper, this complex system and function of the salivary defense proteins will be reviewed.     

Identification of Host Cellular Protein Substrates of SARS-COV-2 Main Protease

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of coronavirus disease-19 (COVID-19) being associated with severe pneumonia. Like with other viruses, the interaction of SARS-CoV-2 with host cell proteins is necessary for successful replication, and cleavage of cellular targets by the viral protease also may contribute to the pathogenesis, but knowledge about the human proteins that are processed by the main protease (3CLpro) of SARS-CoV-2 is still limited. We tested the prediction potentials of two different in silico methods for the identification of SARS-CoV-2 3CLpro cleavage sites in human proteins. Short stretches of homologous host-pathogen protein sequences (SSHHPS) that are present in SARS-CoV-2 polyprotein and human proteins were identified using BLAST analysis, and the NetCorona 1.0 webserver was used to successfully predict cleavage sites, although this method was primarily developed for SARS-CoV. Human C-terminal-binding protein 1 (CTBP1) was found to be cleaved in vitro by SARS-CoV-2 3CLpro, the existence of the cleavage site was proved experimentally by using a His₆-MBP-mEYFP recombinant substrate containing the predicted target sequence. Our results highlight both potentials and limitations of the tested algorithms. The identification of candidate host substrates of 3CLpro may help better develop an understanding of the molecular mechanisms behind the replication and pathogenesis of SARS-CoV-2.     

Heterogeneous asymmetric reactions. 23. Enantioselective hydrogenation of ethyl pyruvate over cinchonine- and α-isocinchonine-modified platinum catalysts

The enantioselective hydrogenation of ethyl pyruvate to (S)-ethyl lactate over cinchonine- and -isocinchonine-modified Pt/Al₂O₃ catalysts was studied as a function of modifier concentration and reaction temperature. The maximum enantioselectivities obtained under the applied mild conditions were 89% ee using cinchonine (0.014 mmoldm^–3, 1 bar H₂, 23°C, 6% AcOH in toluene), and 76% ee in the case of -isocinchonine (0.14 mmoldm^–3, 1 bar H₂, –10°C, 6% AcOH in toluene). Since -isocinchonine of rigid structure exists only in anti-open conformation these data provide additional experimental evidence to support the former suggestion concerning the dominating role of anti-open conformation in these cinchona-modified enantioselective hydrogenations.     

Challenges in Discovering Drugs That Target the Protein–Protein Interactions of Disordered Proteins

Protein–protein interactions (PPIs) outnumber proteins and are crucial to many fundamental processes; in consequence, PPIs are associated with several pathological conditions including neurodegeneration and modulating them by drugs constitutes a potentially major class of therapy. Classically, however, the discovery of small molecules for use as drugs entails targeting individual proteins rather than targeting PPIs. This is largely because discovering small molecules to modulate PPIs has been seen as extremely challenging. Here, we review the difficulties and limitations of strategies to discover drugs that target PPIs directly or indirectly, taking as examples the disordered proteins involved in neurodegenerative diseases.     

Analysis of the Influence of Processing Conditions on the Supramolecular Structure and Antioxidant Distribution in PP‐Pipes Using Infrared Microscopy

The supramolecular structure in pipe walls of isotactic PP‐R is a function of compound composition and processing parameters, which both influence the mechanical properties of the pipes. µFTIR shows a gradient of the crystallinity across the pipe wall, with a lower‐crystalline outer layer, and a higher‐crystalline core layer. The rate of extrusion has an influence on the thickness of the outer layer. The nucleating effect on the morphological profile throughout the pipe wall can be visualised. µFTIR shows a homogeneous distribution of the primary antioxidant in the pipe wall. Both the spectral crystallinity and the antioxidant concentration distribution are calculated.