哪些动物能发光?它们又是怎样发光的呢?

哪些动物能发光?它们又是怎样发光的呢?
哪些动物能发光?它们又是怎样发光的呢?

哪些动物能发光?它们又是怎样发光的呢?
一些海洋动物可发光,如水母、深海鱼类、乌贼等；昆虫中的萤火虫可发光.海洋动物依靠色素发光,萤火虫体内有荧光酶,被ATP激发可发光,是一种冷光源.

萤火虫：体内的萤光素在萤光素酶和ATP的能作用下发光。
电鳐：ATP生物电。
水母：折射光。

萤火虫就可以发光的，萤火虫的发光，简单来说，是荧光素（luciferin）在催化下发生的一连串复杂生化反应；而光即是这个过程中所释放的能量。

一些海洋动物发光依靠绿色荧光蛋白，绿色荧光蛋白的发光机理（图发不上来，我把该综述全文发到百度文库里，全文有绿色荧光蛋白的结构、功能、折叠和基因表达等）
“Primary Sequence from Cloning
The sequence of wild-type Aequorea GFP (10) is given in Figure 1. Sequences
of at...

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一些海洋动物发光依靠绿色荧光蛋白，绿色荧光蛋白的发光机理（图发不上来，我把该综述全文发到百度文库里，全文有绿色荧光蛋白的结构、功能、折叠和基因表达等）
“Primary Sequence from Cloning
The sequence of wild-type Aequorea GFP (10) is given in Figure 1. Sequences
of at least four other isoforms are known (19), though none of themutations seem
to be in positions known to influence protein behavior. Most cDNA constructs
derived fromthe original sequence contain the innocuousmutationQ80R, prob-
ably resulting from a PCR error (11). Also, the gene has been resynthesized
with altered codons and improved translational initiation sequences (see section
on “Promoters, Codon Usage, and Splicing”).
The chromophore is a p-hydroxybenzylideneimidazolinone (10, 20) formed
from residues 65–67, which are Ser-Tyr-Gly in the native protein. Figure 2
shows the currently accepted mechanism (21–23) for chromophore forma-
tion. First, GFP folds into a nearly native conformation, then the imidazoli-
none is formed by nucleophilic attack of the amide of Gly67 on the carbonyl
of residue 65, followed by dehydration. Finally, molecular oxygen dehydro-
genates the ®-¯ bond of residue 66 to put its aromatic group into conjugation
with the imidazolinone. Only at this stage does the chromophore acquire vis-
ible absorbance and fluorescence. This mechanism is based on the following
arguments: (a) Atmospheric oxygen is required for fluorescence to develop
(21, 24). (b) Fluorescence of anaerobically preformed GFP develops with a
simple exponential time course after air is readmitted (21, 25), which is essen-
tially unaffected by the concentration of the GFP itself or of cellular cofactors.
(c)Analogous imidazolinones autoxidize spontaneously (26). (d ) The proposed
cyclization is isosteric with the known tendency for Asn-Gly sequences to cy-
clize to imides (27). Glycine is by far the best nucleophile in such cyclizations
because of its minimal steric hindrance, and Gly67 is conserved in all known
mutants of GFP that retain fluorescence. (e) Electrospray mass spectra indi-
cate that anaerobically preformed GFP loses only 1 § 4 Da upon exposure
to air, consistent with the predicted loss of two hydrogens (22). This implies
that the dehydration (¡18 Da) must already have occurred anaerobically and
must precede oxidation. ( f ) Reid & Flynn (23) have extensively characterized
the kinetics of in vitro refolding of GFP from bacterial inclusion bodies with
no chromophore, urea-denatured protein with a mature chromophore, and de-
natured protein with a chromophore reduced by dithionite. Renaturation was
measured by development of fluorescence and resistance to trypsin attack. Their
results support the sequential mechanism and provide the rate constants shown
in Figure 2. However, many other aspects of the maturation mechanism re-
main obscure, such as the steric and catalytic roles of neighboring residues, the
means by which mutations can improve folding efficiency, and the dependence
of oxidation rate on the oxygen concentration and the protein sequence.
One predicted consequence of oxidation by O2 is that hydrogen peroxide,
H2O2, is presumably released in 1:1 stoichiometry with mature GFP. This
byproduct might explain occasions when high-level expression of GFP can
be deleterious. Perhaps catalase could be useful in such cases. Some difficult
GFPs seemto expressmost readilywhen targeted to peroxisomes andmitochondria (28; R Rizzuto, T Pozzan, personal communication).”
----------from: Roger Y. Tsien,THE GREEN FLUORESCENT
PROTEIN,Annu. Rev. Biochem. 1998. 67:509–44

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