Biomedical Engineering Reference
In-Depth Information
exposed to light in the blue to ultraviolet range [1, 2]. Although many other
marine organisms have similar green l uorescent proteins, GFP tradition-
ally refers to the protein i rst isolated from the jellyi sh Aequorea victoria.
h e GFP from A. victoria has a major excitation peak at a wavelength of 395
nm and a minor one at 475 nm. Its emission peak is at 509 nm, which is in
the lower green portion of the visible spectrum. h e l uorescence quantum
yield (QY) of GFP is 0.79. h e GFP from the sea pansy (Renilla reniformis)
has a single major excitation peak at 498 nm.
h e Y66F GFP, or BFPF, is a blue-shit ed variant of the parent GFP
obtained by replacing Tyr
66
with phenylalanine [3-5]. h us, the aim of this
work is to do a comparative study of the performance of the M06 family of
density functionals for the description of the molecular structure, infrared
(IR) and absorption (UV-Vis), and ECD spectra as well as the chemical
reactivity of the BFPF Green Fluorescent Protein Chromophore.
Knowledge of the reactivity on a molecule is an essential concept; it is of
crucial interest because it allows us to understand interactions that are oper-
ating during a reaction mechanism. In particular, electrostatic interactions
have been successfully explained by the use of the molecular electrostatic
potential [6, 7].
On the other hand, there is not a unique tool to quantify and ratio-
nalize covalent interactions. However, since 2005 a descriptor of local
reactivity, whose name is simply dual descriptor [8, 9], has allowed to
rationalize reaction mechanisms in terms of overlapping nucleophilic
regions with electrophilic regions in order to get a maximum stabiliza-
tion, thus leading to i nal products or intermediates; all those favorable
nucleophilic-electrophilic interactions have been explained as a mani-
festation of the Principle of Maximum Hardness [10]. In addition, chem-
ical reactions are understood in terms of the Hard and Sot Acids and
Bases Principle [11-14], a principle that has been used even with the
aim of replacing the use of the Molecular Orbital h eory to understand
the whole Chemistry [15]. In fact, the present work is a good chance to
test the capability of the most recent reactivity descriptors coming from
the Conceptual DFT [16-19], therefore the framework of this conceptual
theory will be presented in the next section.
7.2 h
eory and Computational Details
At a local level, electronic density is the i rst local reactivity descriptor to
be used when electrostatic interactions are predominant between molecules;
within the framework of Conceptual DFT it is dei ned as follows:
