A Dirac-type Characterization of k-chordal Graphs

Characterization of k-chordal graphs based on the existence of a "simplicial path" was shown in [Chv{\'a}tal et al. Note: Dirac-type characterizations of graphs without long chordless cycles. Discrete Mathematics, 256, 445-448, 2002]. We give a characterization of k-chordal graphs which is a generalization of the known characterization of chordal graphs due to [G. A. Dirac. On rigid circuit graphs. Abh. Math. Sem. Univ. Hamburg, 25, 71-76, 1961] that use notions of a "simplicial vertex" and a "simplicial ordering".Comment: 3 page

Organic Farming in India and its Way Forward

India is home to 30% of the world’s organic growers and is likely to expand in the coming years. The solutionto the issues of sustainability, global warming, land degradation and food security is Organic Farming, which is seen as a sign of dynamic change for the agricultural industry. Organic Farming discards the use of synthetic fertilizers and promotes sustainable agricultural practices. Organic Farming holds immense potential to revive the degrading state of the agricultural sector in the world by offering environmental benefits, quality products and conserving non-renewable resources. It is a promising alternative to conventional farming and is expanding quickly. Organic Farming is gaining worldwide attention with 2.30 million hectares of land being used for the purpose. It helps to reduce greenhouse gas (GHG) emissions and improves soil fertility, boosting productivity and crop health. Organic Farming can also be used for land reclamation purposes. The aim of the present study is to examine the development of Organic Farming in India and globally, as well as identify any potential barriers to its implementation

Molecular docking analysis on 16 therapeutic ligands of Ocimum tenuiflorum L. (Tulasi) and their prospects in drug design for COVID-19

The PyRx software and Discovery studio were used in the present molecular docking studies of the 16 ligands of Ocimum tenuiflorum L., selected based on their high therapeutic potentials, viz., (E)-6-hydroxy-4,6-dimethylhept-3-en-2-one, Apigenin, Bieugenol, Cirsilineol, Cirsimaritin, β-Caryophyllene epoxide, Dehydrodieugenol B, Eugenol, Ferulaldehyde, Isothymonin, Isothymusin, Linalool, Luteolin, Ocimarin, Rosmarinic acid, and Thymol. Saquinavir was used as a positive control. The binding affinities of the 16 ligands to the main proteases of COVID-19 6LU7 and 6Y2E (critical for viral replication) and their ability to arrest the virus replication were recorded. The binding affinities of the ligands to 6LU7 and 6Y2E ranged from -4.3 and -4.7 kcal/mol (for (E)-6-hydroxy-4,6-dimethylhept-3-en-2-one) to -7.6 (for Rosmarinic acid to both target proteins). While the corresponding values for the control drug Saquinavir were -7.8 and -7.6 respectively. The Rosmarinic acid, in binding with both the proteases (-7.6 and -7.6 kcal/mol) showed six conventional hydrogen bonds, one carbon hydrogen bond (ASP 153 had one conventional hydrogen bond and one carbon hydrogen bond), one Pi-alkyl bond, one Pi-Pi stacked bond, eight van der waals bonds for 6LU7 protease; it formed three conventional hydrogen bonds, two Pi-alkyl bonds, one unfavourable donor – donor bond and 14 van der waals bonds with 6Y2E protease. The control drug – Saquinavir in binding with 6LU7 protease showed 12 van der waals, one alkyl, one Pi-alkyl, one Pi-cation, one Pi-stacked and four conventional hydrogen bonds, which indicates that it has less affinity when compared with Rosmarinic acid. Similarly, the control drug on binding with 6Y2E protease exhibited ten van der waals, four Pi-alkyl, one cation and three hydrogen bonds. The results are in conformity to similar other studies, and herald a promising scope for Rosmarinic acid as lead molecule in the drug discovery for COVID-19

Understanding the Cooperative Interaction between Myosin II and Actin Cross-Linkers Mediated by Actin Filaments during Mechanosensation

AbstractMyosin II is a central mechanoenzyme in a wide range of cellular morphogenic processes. Its cellular localization is dependent not only on signal transduction pathways, but also on mechanical stress. We suggest that this stress-dependent distribution is the result of both the force-dependent binding to actin filaments and cooperative interactions between bound myosin heads. By assuming that the binding of myosin heads induces and/or stabilizes local conformational changes in the actin filaments that enhances myosin II binding locally, we successfully simulate the cooperative binding of myosin to actin observed experimentally. In addition, we can interpret the cooperative interactions between myosin and actin cross-linking proteins observed in cellular mechanosensation, provided that a similar mechanism operates among different proteins. Finally, we present a model that couples cooperative interactions to the assembly dynamics of myosin bipolar thick filaments and that accounts for the transient behaviors of the myosin II accumulation during mechanosensation. This mechanism is likely to be general for a range of myosin II-dependent cellular mechanosensory processes

Mechanoaccumulative elements of the mammalian actin cytoskeleton

To change shape, divide, form junctions, and migrate, cells reorganize their cytoskeletons in response to changing mechanical environments [1-4]. Actin cytoskeletal elements, including myosin II motors and actin crosslinkers, structurally remodel and activate signaling pathways in response to imposed stresses [5-9]. Recent studies demonstrate the importance of force-dependent structural rearrangement of α-catenin in adherens junctions [10] and vinculin's molecular clutch mechanism in focal adhesions [11]. However, the complete landscape of cytoskeletal mechanoresponsive proteins and the mechanisms by which these elements sense and respond to force remain to be elucidated. To find mechanosensitive elements in mammalian cells, we examined protein relocalization in response to controlled external stresses applied to individual cells. Here, we show that non-muscle myosin II, α-actinin, and filamin accumulate to mechanically stressed regions in cells from diverse lineages. Using reaction-diffusion models for force-sensitive binding, we successfully predicted which mammalian α-actinin and filamin paralogs would be mechanoaccumulative. Furthermore, a Goldilocks zone must exist for each protein where the actin-binding affinity must be optimal for accumulation. In addition, we leveraged genetic mutants to gain a molecular understanding of the mechanisms of α-actinin and filamin catch-bonding behavior. Two distinct modes of mechanoaccumulation can be observed: a fast, diffusion-based accumulation and a slower, myosin II-dependent cortical flow phase that acts on proteins with specific binding lifetimes. Finally, we uncovered cell-type and cell-cycle-stage-specific control of the mechanosensation of myosin IIB, but not myosin IIA or IIC. Overall, these mechanoaccumulative mechanisms drive the cell's response to physical perturbation during proper tissue development and disease