Hello,
Recently I have acquired 25 mg of phycocyanobilin (PCB) from Santa Cruz Biotechnology, and I am trying to create a stock solution for some optogenetics experiments.
The problem is that I can't seem to properly dissolve it at the reported solubility values, and repeatedly find crystals of the compound after incubating my cells with the PCB.
I have dissolved PCB in DMSO, and taken it to concentrations lower that 1 mg/mL (the solubility reported by Santa Cruz), I´ve tried applying temperature up to 60°C in water baths and thermomixers, and even multiple rounds of sonication. But after a while, my stock solutions end up with that dark-green precipitate at the bottom of the tube.
Maybe someone has experienced a similar problem with phycocyanobilin or maybe, with some other difficult to dissolve compound. Any insight would be greatly appreciated!
Diego Fermoso
Hello! It seems you're having some difficulties with the solubility of phycocyanobilin (PCB), which is a common challenge in optogenetic experiments, especially when working with low concentrations.
The problem you're describing with precipitation is often caused by solubility issues, but it can also happen due to other factors like pH of the solution or the presence of other components in the medium. Here are a few tips that might help:
I hope these tips help you solve the solubility issue and achieve a stable solution for your experiments.
Please work out the experiment with different concentrations of DMSO, surely it will fit in a particular level
Phycocyanobilin (PCB) may not dissolve in DMSO at the reported solubility due to several factors:
1. Aggregation and Self-Association:
• PCB is a tetrapyrrole chromophore that can form aggregates due to strong intermolecular interactions (π-π stacking and hydrogen bonding).
• These aggregates may reduce solubility in DMSO, especially at higher concentrations.
2. Moisture Sensitivity:
• PCB is sensitive to water, which may be present as trace amounts in DMSO.
• Even small amounts of water can lead to partial precipitation or formation of insoluble aggregates.
3. Structural Conformations:
• PCB has multiple tautomeric and conformational states.
• Certain conformations may have reduced solubility in DMSO compared to other solvents.
4. Degradation or Oxidation:
• If PCB is exposed to light or air, it may undergo oxidation or degradation, forming insoluble byproducts.
• Storing PCB under an inert atmosphere and in the dark can help maintain solubility.
Solutions to Improve Solubility:
• Mild Heating: Slightly warming the DMSO (e.g., 40–50°C) can enhance solubility.
• Sonication: Brief ultrasonication can help disperse aggregates.
• Lower Concentration: Start with a lower concentration and gradually increase.
• Alternative Solvents: Consider methanol, ethanol, or DMF, which may better solubilize PCB.
• Use of Additives: Small amounts of a co-solvent like water or a mild base (e.g., NaOH in trace amounts) may improve solubility by altering the hydrogen-bonding network.
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