Biology Reference
In-Depth Information
bu
V
ering near the higher end. Note that the lower a
Y
nity bu
V
ers typically have
-rates and thus equilibrate faster and damp rapid [Ca
2
þ
] spikes more
higher o
V
e
V
ectively.
5. Why Use Software and Where to Get MaxChelator?
Despite all the caveats, using software to calculate free [Ca
2
þ
], [Mg
2
þ
], and [Mg-
ATP] is necessary to have a reasonable chance of getting the solutions right. And
we think that MaxChelator is a useful tool in this regard. More information and
downloads (free) are available at
http://maxchelator.stanford.edu/
.
Whenever
practical, it is also highly desirable to measure the [Ca
2
þ
] using either electrodes
or fluorescent Ca
2
þ
indicators to confirm the predictions and check for reproduc-
ibility. These measurements are less practical for other metals (even Mg
2
þ
)or
anions, for which electrodes and fluorescent indicators are less available.
6. MaxChelator for Windows
The earliest MaxChelator e
ort was a DOS program which was then moved to
Windows (Winmaxc), and the latest version is posted at the above website. The
current Windows version allows visualization in two or three dimensions, some of
the key factors that a
V
ect the result. The source code is hundreds of pages long and
is complied under the Delphi (Visual Pascal) environment (not posted). The files of
constants are editable using a text editor and any number of files of constants can
be maintained. However, the algorithms used to calculate the e
V
ects of tempera-
ture and ionic concentration are hidden, limiting the flexibility of this version. On
the other hand, it is straightforward to use and multiple metals and chelators can
be easily used together (e.g., Ca
2
þ
,Mg
2
þ
,Ba
2
þ
, BAPTA, Br
2
BAPTA, and ATP).
V
7. Javascript Web Versions
Not everyone wants to use windows software, so the algorithms have been
ported to Javascript which runs on all platforms that have a browser with Java-
script enabled (with syntax similar to C programming language). One limitation is
that the math libraries for interpreted Javascript are not as accurate as those for
compiled programs (and rounding errors can create limitations, especially with
simultaneous use of multiple metals and chelators). Some people also disable
Javascript because of the fear of malware.
An advantage of Javascript, besides running on most computers, is that the
source code is readily accessible and can be saved, edited, and then run on any
machine. If the result is an improvement, it can be shared. Another advantage is
the simple user interface. Everything is in front of you all the time, and it is very
easy and intuitive to change pH, temperature, ionic concentration, or metal/
chelator concentrations. Several variants are available for either online calcula-
tions or download. Some are simple binary Ca-EGTA or Mg-ATP calculators like
