PMC

Comparison of the Guanidine Binding Sites of the Three Classes of Guanidine Riboswitch Structures
The nucleotides have been colored to reflect their function in ligand binding. Guanine bases accepting hydrogen bonds from guanidine at O6 and N7 on the Hoogsteen edge are green (all classes), guanine bases making hydrogen bonds to O6 alone (A guanidine I riboswitch) are blue, nucleotides only making backbone contacts (B guanidine II riboswitch) are gray, and nucleotides making π-cation interaction with the guanidinium cations (all classes) are yellow. The image of the guanidine I riboswitch was prepared using PDB: 5T83 (), and that of the guanidine II riboswitch (P1 stem-loop) was prepared using PDB: 5NDI (). The guanidine III riboswitch (C) is the present work.

PCR for Chagas disease HSROC - subgroups of blood samples boiled before processed and stored with guanidine. Big blue upside down triangle - summary estimate of the group stored with guanidine and boiled; Big green diamond - summary estimate of the group stored with guanidine and not boiled; Big red triangle - summary estimate of the group not stored with guanidine and not boiled; Blue small squares and blue small upside down triangles - shrunken estimates from bivariate model and crude estimates (respectively) from group stored with guanidine and not boiled; blue solid line - SROC curve from group stored with guanidine and boiled; dot - crude estimates; small green squares and small green diamonds - shrunken estimates from bivariate model and crude estimates (respectively) from group stored with guanidine and not boiled; solid green line - SROC curve from group stored with guanidine and not boiled; small red squares and small red triangles - shrunken estimates from bivariate model and crude estimates (respectively) from group not stored with guanidine and not boiled; red solid line - SROC curve from group not stored with guanidine and not boiled; NA - not assigned or missing.

Curing of [PSI⁺] by Hsp104 overexpression when severing is inhibited by guanidine. (A) Curing of [PSI⁺] by guanidine inactivation in the presence and absence of high concentrations of Hsp104. By using a Δsti1 strain derived from 779-6A, [PSI⁺] yeast was transformed with the vector control or a plasmid expressing Hsp104 from the GAL1 promoter. [PSI⁺] cells were cured in SGal medium with and without guanidine. Curing data are from yeast cells grown in 5 mM guanidine with endogenous levels of Hsp104 or in yeast cells overexpressing (o/e) Hsp104. The curing of [PSI⁺] in yeast cells overexpressing Hsp104 in the absence of guanidine is shown by the dashed line. (B) Curing of [PSI⁺] by Hsp104 overexpression from the GAL1 promoter was performed in the presence and absence of 5 mM guanidine in strain 1074. The solid symbols are data obtained in the presence of guanidine, and the open symbols are data obtained in the absence of guanidine. (C) Curing of [PSI⁺] by Hsp104 overexpression from the GAL1 promoter was performed in the presence and absence of guanidine in strain 779-6A. The solid symbols are data obtained in the presence of guanidine, and the open symbols are data obtained in the absence of guanidine. Data points were obtained from three independent experiments under each experimental condition.

A, D, G Time-course of slope fEPSP recorded from control slices in CA1 region, 10 min before and 20 min after bath application of increasing concentrations of Guanidine. Guanidine induces a dose-dependent increase in the fEPSP evoked in CA1 region (two-way ANOVA: Guanidine 100 µM, n = 4, F_(9,54) = 4.89, pre vs post 16, 18, and 20 min, Bonferroni post hoc *p < 0.05, **p < 0.01; Guanidine 1 mM, n = 6, F_(9,90) = 30.14, pre vs post 1–20 min, Bonferroni post hoc ***p < 0.001). Next to the graphs, representative traces of fEPSP PRE, 10 and 20 min after Guanidine application. Scale factor is 5 ms/0.2 mV for all traces. B, E, H Input/output (I/O) curves, representing variations in the fEPSP slope in response to the increasing stimulus intensity, show enhanced excitability of the CA1 fEPSPs following Guanidine application (two-way ANOVA time × group interaction: Control PRE vs Guanidine 100 µM, n = 7, F_(8,96) = 13.68, 13–16 V, Bonferroni post hoc *p < 0.05, **p < 0.01, ***p < 0.001; Control PRE vs Guanidine 1 mM, n = 7, F_(8,88) = 3.86, 13–16 V, Bonferroni post hoc *p < 0.05, **p < 0.01, ***p < 0.001). C, F, I Upper part; sample traces of paired fEPSPs in response to two sequential presynaptic stimuli at an interval of 60, 100, 200, and 300 ms recorded in CA1 region. Scale bars is 5 ms/0.2 mV for all traces. Graphs represent PPR before and after Guanidine 1 µM, 100 µM, and 1 mM application showing that at the 60 ms and 100 ms interval between pulses, there is a decrease in PPR parameter (two-way ANOVA time × group interaction: Control PRE vs Guanidine 100 µM, n = 8, F_(3,36) = 1.67, 60 ms and 100 ms, Bonferroni post hoc *p < 0.05; two-way ANOVA time × group interaction: Control PRE vs Guanidine 1 mM, n = 5, F_(3,24) = 20.89, 60 ms and 100 ms, Bonferroni post hoc ***p < 0.001). By contrast, the smaller dose of Guanidine (1 µM) did not alter the S2/S1 ratio (C).