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紫外線燈下的雞蛋為什么會發紅色熒光?

作者:luyor時間:2020-06-18 22:31瀏覽2455 次

信息摘要:

紫外線下雞蛋的紅色發光或熒光是由于在蛋殼中發現的特定分子引起的。該分子是原卟啉IX(PPIX)。PPIX是血紅蛋白的前體,是使我們的血液(和雞的血液)呈現紅色的色素。那么,該分子如何進入蛋殼?

紫外線燈照射雞蛋上。蛋殼會發出紅色光芒。是什么導致這種紅色發光?這就是該圖形的外觀!

紫外線下雞蛋的紅色發光或熒光是由于在蛋殼中發現的特定分子引起的。該分子是原卟啉IX(PPIX)。PPIX是血紅蛋白的前體,是使我們的血液(和雞的血液)呈現紅色的色素。那么,該分子如何進入蛋殼?

雞蛋在紫外線燈下發出紅色熒光


PPIX通過特定酶的作用轉化為血紅蛋白的非蛋白質成分血紅素。在包括雞在內的某些鳥類的輸卵管中,該酶的活性較低。至于這樣做的結果,PPIX 被合并到蛋殼,賜給他們的棕褐色。
 
PPIX使蛋殼在紫外線下發出熒光。熒光是由于PPIX分子中的電子吸收了紫外線。這將電子推向短暫的更高能量的“激發態”。首先,一些多余的能量例如作為熱量損失到周圍環境中。然后,電子回落到它們的原始能級,從而消除了多余的能量,即可見光。這被視為熒光。從開始到結束,整個過程超過了十億分之一秒。
 
這里對熒光的過程有更詳細的解釋。下圖顯示了PPIX二甲基酯的熒光(之所以使用,是因為它具有更好的溶解性和穩定性)。下面的圖像(以及主圖中的圖像)由Hannes Hiller提供,后者在MicroXtals 分享了漂亮的化學圖像。

雞蛋發出熒光原理 
雞蛋熒光化學pt 2
 
注意:使用紫外線燈重現本文中圖片中看到的熒光應該沒有問題。請注意,如果要在實驗室中重現效果,則實驗室中使用的常規UV-A光源為365 nm –該波長不足,因為PPIX在該波長附近幾乎沒有吸收。因此,重要的是要使用“廉價”的紫外光源(395至405 nm)來再現結果!

雞蛋檢查
紫外線檢查燈用于散養雞蛋的質量控制檢查,以檢測是否有清洗或擦拭的跡象,并突出顯示細菌和霉菌造成的腐敗。目前已被DEFRA雞蛋檢驗員,孵化場,雞蛋包裝中心,批發商和食品加工商使用。
Egg Inspection
UV inspection lamps are used for quality control inspection of free-range eggs to detect evidence of washing or wiping and highlighting spoilage by bacteria and mold. Currently used by DEFRA egg inspectors, hatcheries, egg packing centers, wholesalers and food processors.

雞蛋發出熒光原理

What makes eggs glow under UV light?

Here’s something to try over the Easter weekend: take a UV light and shine it on some eggs. You’ll be rewarded with a red glow from their shells. What causes this red glow? That’s what this graphic looks at!

The red glow, or fluorescence, of eggs under a UV light is due to a particular molecule found in egg shells. This molecule is protoporphyrin IX (PPIX). PPIX is a precursor of haemoglobin, the pigment that gives our blood (and that of chickens) its red colour. How, then, does this molecule get on to eggshells?

PPIX converts into haem, the non-protein component of haemoglobin, by the action of a particular enzyme. This enzyme’s activity is low in the oviduct of some birds, including chickens. As a consequence of this, PPIX is incorporated into egg shells, given them their brown colour.
 
PPIX causes egg shells to fluoresce under UV light. The fluorescence is due to electrons in PPIX molecules absorbing the UV light. This pushes the electrons to a higher energy ‘excited state’, which is short-lived. First, some of the excess energy is lost to the surroundings, for example as heat. Then, the electrons fall back to their original energy level, getting rid of their excess energy as visible light. This is seen as fluorescence. From start to finish, the whole process is over in billionths of a second.
 
There’s a more detailed explanation of the process of fluorescence here. The image below shows the fluorescence of the dimethyl ester of PPIX (used because it has better solubility and stability). The images below (and those in the main graphic) were kindly provided by Hannes Hiller, who shares beautiful chemistry images over at MicroXtals.
 
 
Note: You should have no problem with using UV torches to reproduce the fluorescence seen in the pictures in this post. Note that if you’re trying to reproduce the effect in a laboratory, the normal UV-A light source used in labs is 365 nm – this wavelength is insufficient because PPIX has almost no absorption around this wavelength. So it’s important to use the “cheap” UV sources (395 to 405 nm) to reproduce the results!

 紫外線手電筒LUYOR-2130L

用于檢查雞蛋質量的紫外線手電筒LUYOR-2130L


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