I know some workers stirring the PFA solution overnight and then filter.
2008-12-09 tf 发件人: Merced Leiker 发送时间: 2008-12-09 01:18:55 收件人: [EMAIL PROTECTED] 抄送: histonet@lists.utsouthwestern.edu; Tony Henwood 主题: RE: [Histonet] PFA preparation: Does dissolution also mean thatthe PFA has depolymerized? Yes, we would say that heating is not necessary to depolymerize PFA. Only the high pH is. After 30-60 minutes of stirring we obtain a crystal clear solution with only a few particles of undissolved PFA swimming around at the bottom (which is why we filter). --On Monday, December 08, 2008 9:19 AM -0700 [EMAIL PROTECTED] wrote: > Hi Merced, > > Thanks for your reply. So then you manipulate pH rather than temperature > to ensure the dissolution of PFA. Does dissolution also mean that the PFA > has depolymerized? Are you saying heating to 60 degrees C is not required, > or that it is not recommended? I've been told that heating 'degrades' the > PFA and one wants to avoid this. But according to other sources, the > heating step is required to ensure that the PFA does in indeed degrade, > degrade into formaldehyde. > > Eric > > University of Calgary > Medical Sciences > > >> > We routinely add paraformaldehyde to alkaline water at room temperature >> while stirring and wait only about 30-60 mintues for it to dissolve. >> Then we add a concentrated amount of PBS up to the total required volume >> (so that the buffer is 1x in the final volume). Then we add acid to >> bring the pH back down to 7. Then we filter it since not all of the PFA >> has dissolved (though most of it has). >> >> Merced >> >> --On Monday, December 08, 2008 9:11 AM +1100 Tony Henwood >> <[EMAIL PROTECTED]> wrote: >> >>> My experience is that when you add paraformaldehyde to water all it >>> forms is a colloidal solution (ie on standing, the paraformaldehyde >>> settles with very little going into solution (personal experience, >>> waited one week, then gave up). >>> >>> Has your experience been different? >>> >>> Regards >>> >>> Tony Henwood JP, MSc, BAppSc, GradDipSysAnalys, CT(ASC) >>> Laboratory Manager & Senior Scientist >>> Tel: 612 9845 3306 >>> Fax: 612 9845 3318 >>> the children's hospital at westmead >>> Cnr Hawkesbury Road and Hainsworth Street, Westmead >>> Locked Bag 4001, Westmead NSW 2145, AUSTRALIA >>> >>> >>> >>> >>> -----Original Message----- >>> From: [EMAIL PROTECTED] >>> [mailto:[EMAIL PROTECTED] On Behalf Of >>> [EMAIL PROTECTED] >>> Sent: Sunday, 7 December 2008 7:30 AM >>> To: histonet@lists.utsouthwestern.edu >>> Subject: [Histonet] PFA preparation >>> >>> >>> Hi, >>> >>> So then what is the best way to prepare formaldehyde fixative from >>> PFA? >>> >>> The way I have been taught, which differs from what I have read, is >>> to dissolve 4% into ddH2O at room temperature. After that one could add >>> PBS or buffer. >>> >>> I've also been taught that too much heat during preparation >>> "degrades" PFA, and that PFA (or formaldehyde solution, rather) stored >>> too long will lose freshness because it "degrades." >>> >>> What I read is different. Texts suggest to dissolve the PFA in warm >>> water, and that aging of the fix is due to repolymerization, not >>> through >>> degradation. >>> >>> What should i do? >>> >>> Eric Schmidt >>> >>> University of Calgary >>> Medical Sciences >>> >>> >>> >>> >>> _______________________________________________ >>> Histonet mailing list >>> Histonet@lists.utsouthwestern.edu >>> http://lists.utsouthwestern.edu/mailman/listinfo/histonet >>> >>> ********************************************************************* >>> This email and any files transmitted with it are confidential and >>> intended solely for the use of the individual or entity to whom they >>> are >>> addressed. If you are not the intended recipient, please delete it and >>> notify the sender. >>> >>> Views expressed in this message and any attachments are those of the >>> individual sender, and are not necessarily the views of The Children's >>> Hospital at Westmead >>> >>> This note also confirms that this email message has been >>> virus scanned and although no computer viruses were detected, The >>> Childrens Hospital at Westmead accepts no liability for any >>> consequential >>> damage resulting from email containing computer viruses. >>> ********************************************************************** >>> >>> >>> _______________________________________________ >>> Histonet mailing list >>> Histonet@lists.utsouthwestern.edu >>> http://lists.utsouthwestern.edu/mailman/listinfo/histonet >>> >> >> >> >> Merced M Leiker >> Research Technician II >> 354 BRB (pkgs) / 140 Farber Hall (letters) >> School of Medicine and Biomedical Sciences >> State University of New York at Buffalo >> 3435 Main St, Buffalo, NY 14214 >> Ph: (716) 829-6033 >> Fx: (716) 829-2725 >> >> "Without my flaws I'm really very boring." >> - random internet blog commentator >> >> >> > > > Merced M Leiker Research Technician II 354 BRB (pkgs) / 140 Farber Hall (letters) School of Medicine and Biomedical Sciences State University of New York at Buffalo 3435 Main St, Buffalo, NY 14214 Ph: (716) 829-6033 Fx: (716) 829-2725 "Without my flaws I'm really very boring." - random internet blog commentator _______________________________________________ Histonet mailing list Histonet@lists.utsouthwestern.edu
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