BIS-TRIS buffer

Activation of the M. citricolor luciferin precursor with decylamine. The following mixture was incubated overnight at room temperature (23 24°C) luciferin precursors before the separation of isomers by F1PLC (50 pi, activity 2 x 1012 photons by the assay method described above), 30 mM Bis-tris buffer (pH 6.4, 4.5 ml) acetonitrile... 

The results discussed here have confirmed our earlier conclusions that (1) in the absence of organic phosphate (i.e., in 0.1 M Bis—Tris buffer), there is no preferential 02 binding to the a or 0 chains of Hb A, and (2) in the presence of organic phosphate, the a chains have a higher affinity for 02 than do the 0 chains. 

Maillard browning reactions were usually performed by refluxing 0.10 M aqueous phosphate, acetate, succinate or 2,2-bis(hydroxymediyl)-2,2 ,2 -nitrilotrie anol ( bis-tris ) buffer solutions containing various carbohydrates (0.10 M) and p-alanine (0.033 M) for a periods ranging up to 300 min. at... 

Following an 80 min reaction, ribose/phosphate buffer mixtures were rapidly cooled to 25 C, treated with o-phenylenediamine and incubated at 50 C for 30 min. Quinoxalines and unreacted OPD were extracted and concentrated for GC/MS analysis or separation by preparative TLC. Volatile quinoxaline and methylquinoxalines were identified by Rt and MS of available standards. 2-Ethylquinoxaline was tentatively identified by its MS alone. Non-volatile quinoxalines were isolated by preparative TLC and tentatively identified through literature Rf, NMR and UV data. Addition of OPD at die start of ribose/phosphate buffer reactions produced somewhat higher yields of the same quinoxalines in a similar ratio. No evidence for quinoxaline products was found in control experiments run in bis-tris buffer. 

Figure 1. Xylose/P-alanine browning at 10(fC and pH 7.3 in phosphate and bis-tris buffers...

Figure 2. Browning of sugars with /3-alanine after 10(fC/80 min. in phosphate or bis-tris buffer at pH 7.3...

The filtered XlnD fermentation broth was initially concentrated into 20 mM Bis-Tris buffer at pH 6.8 in a 300 ml stirred ultrafiltration cell from Amicon (Beverly, MA) with a 30,000 Da molecular weight cut-off membrane. The protein was then bound to a Source Q anion exchange column (96 ml) and eluted over a 0 to 1 M NaCl gradient into 20 mM Bis-Tris at pH 6.8. The eluted XlnD peak was then reconcentrated and rerun on the Source Q column. From this run, the XlnD fractions were then pooled and buffer-exchanged into 20 mM acetate buffer at pH 5.0 with 100 mM NaCl on a Superdex 200 size exclusion column. The purity of the purified fiactions was assessed by SDS-PAGE, and the protein content was assessed by measuring the absorbance at 280 nm and by bicinchoninic acid (BCA) assay with bovine serum albumin (BSA) run as a standard. 

Figure 3 4 (upper panel) Dependence of the intrinsic f uorescence spectrum of native horse lieart apomyoglobin at pH 6.0 in 10 mM bis-Tris buffer at 21 C on hydrostatic pressure. Hydrostatic pressure values. Obar (solid line), ISObar (dotted line), 600bar (small dashed line) 1000 Bar (dash-double dotted line) 1200 Bar (large dashed line) 1400 Bar (dash-single dotted line), and 2600 Bar (medium dashed line). 

Figure 3.S (lower panel). ( ), Average emission wavelength of native horse heart apomyoglobin at pH 6.0 in 10 mM bis-Tris buffer at 21 C as a function of pressure. ( ). Average emission wavelength for the molten globule state of horse heart apomyoglobin at pH 4.2.10 mM sodium acetate. 21°C. Solid lines represent fits to the data points. Source Vidugiris, G J. A. and Royer. C. A. 1998, Biophysical Journal 75, 463-470. Authorization of reprint accorded by the American Biopliysical Society...

Fig. 7. Time-resolved spectra and difference spectra for the pre-steady state and steady-state phases of the Co(II)E-catalyzed oxidation of benzyl alcohol by NAD at pH 9 (A, C) and pH 4.8 (B, D) and 25° for the wavelength range 300-450 nm. Scanning was carried out as described in the caption to Fig. 5. Difference spectra in (C) and (D) were calculated by subtracting the last spectrum collected in the pre-steady-state phase [respectively spectrum 8 of (A) and spectrum 10 of (B)] from all other spectra in the set. Single-wavelength time courses are shown in insets a and b of (A) and (B). Conditions after mixing were as follows (A, C) [Co(II)E], 29 fiN [NAD+], 1.4 mM [benzyl alcohol], 2 mM [IBA], 50 mAf 50 mM glycine and 50 mM Bis-Tris, final pH 9.0 (B, D) [Co(II)E], 29 fiN [NAD ], 3.5 mM [benzyl alcohol], 4 mM [IBA], 50 mM 10 mM H2SO4 and 50 mM Bis-Tris, final pH 4.8. Reaction was initiated by mixing enzyme in Bis-Tris buffer (pH 6.5) with NAD, benzyl alcohol, and IBA preincubated in the above-indicated solutions. (From Sartorius et al. with permission.) Copyright 1987 American Chemical Society.

In vitro experiments have shown that cyclotetraglucose dissolved in Bis-Tris buffer (50 mmol/l) is not degraded by human salivary or porcine pancreatic a-amylase or by artificial gastric juice (pH 2). Only 0.7% of cyclotetraglucose incurred ring opening during a 3-h incubation period with an acetone powder preparation of the rat intestinal mucosa to form a linear tetrasaccharide (Hashimoto et al., 2006). 

Figure 5.16 CVs obtained for varying (A) BV and (B) MV concentrations in the presence of 1 mM nitrate at the GC/NR electrode in 50 mM Bis-Tris buffer containing 50 mM KCl as electrolyte, pH 7 at a sweep rate of 5 mV s" . Reprinted with permission from ref. 98. Copyright 2013 American Chemical Society.

Based on this work a sensitive and stable electrochemical biosensor for nitrate was constructed using plant NR and the highest potential mediator AQ at a glassy carbon electrode. Amperometry was used to monitor the catalytic nitrate reduction current at the electrode in a homogeneously stirred 50 mM Bis-Tris buffer solution at an applied potential of -400 mV vs. NHE. An initial steady-state current response was observed in the presence of 10 pM nitrate and subsequent nitrate additions at intervals of 100 s led to a step in the current with a steady state reached within ca. 30 s. The steady-state current increased linearly with nitrate concentration from 10 to 70 pM and the detection limit was found to be 0.76 nM (S/N = 3). The practical application of the biosensor was demonstrated by the determination of nitrate... 

Figure 3. Scheme and equilibrium constants for p-amlno-benzoyl-L-glutamate (P) and 2,4-dlamlnopyrlmldlne (D) binding to dlhydrofolate reductase (E) The equilibrium constants were determined by measuring the changes in the fluorescence of the ligand or the enzyme which accompany complex formation. All measurements were made at 25°C in 15 nM Bis-Tris buffer in the presence of 0.5 M KCl. 

PolyCAT A with bis-tris buffers and sodium acetate gradients has been used to separate and quantitate many normal and abnormal Hb components [42,43]. 

---