The kinetic and thermodynamic stabilities of G-quadruplex structures have been extensively studied. In contrast, systematic investigations of the volumetric properties of G-quadruplexes determining their pressure stability are still relatively scarce. The G-rich strand from the promoter region of the c-MYC oncogene (G-strand) is known to adopt a range of conformational states including the duplex, G-quadruplex, and coil states depending on the presence of the complementary C-rich strand (C-strand) and solution conditions. In this work, we report changes in volume, ΔV, and adiabatic compressibility, ΔK S, accompanying interconversions of G-strand between the G-quadruplex, duplex, and coil conformations in the presence and absence of C-strand. We rationalize these volumetric characteristics in terms of the hydration and intrinsic properties of the DNA in each of the sampled conformational states. We further use our volumetric results in conjunction with the reported data on changes in expansibility, ΔE, and heat capacity, ΔC P, associated with G-quadruplex-to-coil transitions to construct the pressure–temperature phase diagram describing the stability of the G-quadruplex. The phase diagram is elliptic in shape, resembling the classical elliptic phase diagram of a globular protein, and is distinct from the phase diagram for duplex DNA. The observed similarity of the pressure–temperature phase diagrams of G-quadruplexes and globular proteins stems from their shared structural and hydration features that, in turn, result in the similarity of their volumetric properties. To the best of our knowledge, this is the first pressure–temperature stability diagram reported for a G-quadruplex.

Requirement Engineering is one of the most crucial tasks because it serves as the foundation for any software. Four pillars of requirement engineering procedures underpin the entire software. The bricks that make up the software edifice are functional and non-functional needs. Finally, design, implementation, and testing add stories to the foundation, allowing a full software tower to be built on top of it. As a result, the foundation must be strong enough to support the remainder of the software tower. Requirement engineers have various hurdles to design successful software for this purpose. Requirement Engineering (RE) is emerging as an increasingly important discipline to promote the development of web applications, as these are designed to meet various stakeholder requirements, additional functional, information, multimedia, and usability requirements compared to traditional software applications. The requirements of software systems are a very important area in software engineering. The success of software systems depends on how it effectively meets the requirements of users. In this paper, the review of current state of requirements engineering in which requirements from users are checked analyzed with their consistency and correctness is presented, and then identifies the emerging models of requirement engineering. Firstly, the paper highlight the current activities that enable the understanding of goals and objectives for developing proposed software systems, then the focus is on the techniques for improving the precision, accuracy, and variety of requirements. Next, identification of the challenges of emerging requirement engineering models is explained. The challenges like security and global trend that posed by emerging models of the future. Finally, we are trying to suggest some solutions for the mentioned challenges.

The G-quadruplex (GQ), a tetrahelix formed by guanine-rich nucleic acid sequences, is a potential drug target for several diseases. Monomolecular GQs are stabilized by guanine tetrads and non-guanine regions that form loops. Hydrostatic pressure destabilizes the folded, monomolecular GQ structures. In this communication, we present data on the effect of pressure on the conformational stability of the tetramolecular GQ, d[5′-TGGGGT-3′]4. This molecule does not have loops linking the tetrads; thus, its physical properties presumably reflect those of the tetrads alone. Understanding the properties of the tetrads will aid in understanding the contribution of the other structural components to the stability of GQ DNA. By measuring UV light absorption, we have studied the effect of hydrostatic pressure on the thermal stability of the tetramolecular d[5′-TGGGGT-3′]4 in the presence of sodium ions. Our data show that, unlike monomolecular GQ, the temperature at which d[5′-TGGGGT-3′]4 dissociates to form the constituent monomers is nearly independent of pressure up to 200 MPa. This implies that there is no net molar volume difference (∆V) between the GQ and the unfolded random-coil states. This finding further suggests that the large negative ∆V values for the unfolding of monomolecular GQ are due to the presence of the loop regions in those structures.

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