Rapid three-dimensional microfluidic mixer for high viscosity solutions to unravel earlier folding kinetics of G-quadruplex under molecular crowding conditions

G-quadruplexes are special structures existing at the ends of human telomeres, the folding kinetics of which are essential for their functions, such as in the maintenance of genome stability and the protection of chromosome ends. In the present study, we investigated the folding kinetics of G-quadruplex in different monovalent cation environments and determined the detailed kinetic parameters for Na+- and K+-induced G-quadruplex folding, and for its structural transition from the basket-type Na+ form to the hybrid-type K+ form. More interestingly, although Li+ was often used in previous studies of G-quadruplex folding as a control ion supposed to have no effect, we have found that Li+ can actually influence the folding kinetics of both Na+- and K+-induced G-quadruplexes significantly and in different ways, by changing the folding fraction of Na+-induced G-quadruplexes and greatly increasing the folding rates of K+-induced G-quadruplexes. The present study may shed new light on the roles of monovalent cations in G-quadruplex folding and should be useful for further studies of the underlying folding mechanism.

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Thermodynamic Stability and Folding Kinetics of the Major G-Quadruplex and Its Loop Isomers Formed in the Nuclease Hypersensitive Element in the Human c-Myc Promoter: Effect of Loops and Flanking Segments on the Stability of Parallel-Stranded Intramolecular G-Quadruplexes

Biochemistry ◽

10.1021/bi100946g ◽

2010 ◽

Vol 49 (43) ◽

pp. 9152-9160 ◽

Cited By ~ 57

Author(s):

Emmanuel Hatzakis ◽

Keika Okamoto ◽

Danzhou Yang

Keyword(s):

Thermodynamic Stability ◽

Folding Kinetics ◽

Promoter Effect ◽

G Quadruplex ◽

The Stability ◽

Kinetics Of

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A Novel Pseudomonas geniculata AGE Family Epimerase/Isomerase and Its Application in d-Mannose Synthesis

Foods ◽

10.3390/foods9121809 ◽

2020 ◽

Vol 9 (12) ◽

pp. 1809

Author(s):

Zhanzhi Liu ◽

Ying Li ◽

Jing Wu ◽

Sheng Chen

Keyword(s):

3D Structure ◽

Three Dimensional ◽

Optimal Temperature ◽

Reaction Conditions ◽

Enzymatic Production ◽

Physiological Properties ◽

Potential Applications ◽

Kinetics Of ◽

Optimal Reaction ◽

Gene Age

d-mannose has exhibited excellent physiological properties in the food, pharmaceutical, and feed industries. Therefore, emerging attention has been applied to enzymatic production of d-mannose due to its advantage over chemical synthesis. The gene age of N-acetyl-d-glucosamine 2-epimerase family epimerase/isomerase (AGEase) derived from Pseudomonas geniculata was amplified, and the recombinant P. geniculata AGEase was characterized. The optimal temperature and pH of P. geniculata AGEase were 60 °C and 7.5, respectively. The Km, kcat, and kcat/Km of P. geniculata AGEase for d-mannose were 49.2 ± 8.5 mM, 476.3 ± 4.0 s−1, and 9.7 ± 0.5 s−1·mM−1, respectively. The recombinant P. geniculata AGEase was classified into the YihS enzyme subfamily in the AGE enzyme family by analyzing its substrate specificity and active center of the three-dimensional (3D) structure. Further studies on the kinetics of different substrates showed that the P. geniculata AGEase belongs to the d-mannose isomerase of the YihS enzyme. The P. geniculata AGEase catalyzed the synthesis of d-mannose with d-fructose as a substrate, and the conversion rate was as high as 39.3% with the d-mannose yield of 78.6 g·L−1 under optimal reaction conditions of 200 g·L−1d-fructose and 2.5 U·mL−1P. geniculata AGEase. This novel P. geniculata AGEase has potential applications in the industrial production of d-mannose.

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