Who knows the answer, please tell me.

If Chinese people in the past patented  paper making, printing and gun powder, what would the world be now?

高中毕业后回母校见过付Sir一次，还是那只布满茶渍的搪瓷杯，还是那位可爱的付Sir。这一面竟成了永别。

在厂猪的Blog上读到消息：“2007年2月21日，农历正月初四，由于感冒去输液之后回家的付老师，突然猝死于家中，医院判断为心脏与肾脏突然衰竭。享年39岁又10个月。” 我和老婆都沉默了。

付Sir大我们10岁，圆圆的娃娃脸，笑起来很腼腆。

PNA - Peptide Nucleic Acid

First obtaining some knowledge, then the creation starts.

Yes, PNAs are synthesized by humans. Although there are some thoughts about ancient life forms using PNA as genetic material, no natural occurring PNA is found in living organisms.

The major chemical difference between DNA/RNA and PNA is the backbone. The backbone of PNA is formed through peptide bonds. The Bases: A, T, G, and C are the same. Therefore PNA can base pair with DNA/RNA. The peptide backbone gives PNA properties different from DNA/RNA. PNA is chemically more stable. Because of this structure difference, enzymes working with DNA/RNA does not recognize PNA. Therefore PNA is also resistant to enzymatic degradation. The complementary base pairing of PNA/PNA or PNA/DNA is stronger and more specific. Interestingly, under conditions (such as temperature, pH, salt) that prevent DNA base pairing, PNA/DNA complex formation will not be impaired. The synthetic PNA makes much better probes for FISH analysis. Some detection techniques have been developed and have been shown very high sensitivity. Currently, limited length of PNA can be synthesized (15~25 bases), and there is also some solubility problems. However, PNA has its potential to used in scientific research and therapies.

One question I eager to know the answer is, if PNA invades double stranded DNA in vivo and forms a very stable PNA/DNA complex. What would the cell react to this complex? Would the complex formation trigger the DNA repair mechanism? (No enzyme in the cell could do anything about PNA, but would the cell simple chop off the complex and replace it?) Would PNA treatment increase the mutation rate of a genome?

Metabolomics - a new growing field of system biology

I attended a seminar yesterday about Metabolomics. The talk was very well organized and the discussions during the talk was really inspiring. Let me put down a simple introduction here in my blog today.

What is Metabolomics? Metabolomics, similar to other "omics", is the SYSTEMATIC study of metabolites. It is actually not a new word, the first paper using this term dated back to 1998. The concept was going all the way back to the 1970s. But more and more attention has be given to this field of study in recent years because of its potential in medical research, diagnostics, drug testing and discovery, nutrition science, agriculture and so on and so forth.

Let us take a look at the "omics" we are talking about all the time nowadays. The first level of system biology, Genomics, studies the genome, which is the "blueprint" of an organism. For example, the human genome contains about 20,000~25,000 genes. Those genes stores all (or almost all) the information that is need for an organism. However, they can not do anything by themselves. They have to be transcribed into RNA. So the next level is the transcriptomics, the study of the transcripts. We are talking about, say, 100,000 transcripts in humans. To actually function, these transcripts need to be further processed. The majority (?) of the transcripts will be translated into different proteins. And here comes the proteomics. Of course, the proteins can be further modified post-transcrptionaly (phorsphorylation, ubiquitination etc.). So the actually number of different proteins in a normal human body would be about 1,000,000.

The trend doesn't look good isn't it? From the blue print (the genome) to the functional units (proteins), the individual elements keep expanding, making it harder and harder to study. Fortunately, no matter how complex an organism could be, the single most important purpose of it is "to live". Metabolism is the characteristic of living. The metabolites we utilize or produce to keep life going are really of limited amount. Therefore, although of millions of proteins are produced, they only tightly control the metabolism of about 3,200 simple chemicals. Among them, about 1,200 are core metabolites.

Metabolites are simple and less complex chemicals. For humans, the biggest metabolite we are dealing with are less than 1,600 in mass (excluding exogenous sources). Majority of the metabolites are between 800 and 1,200 in mass (in terms of abundance). They can be studied quantitatively with less difficulty. I think this is the reason why that at current stage, metabolomics is a more practically approach.

又是一年三十。昨天上午去了家附近的一个购物中心，华人商会在那种搞了不少活动。有舞龙舞狮唱戏的，还有书画摄影展。人很多，热热闹闹的。好久没有过过这样热闹的年了。晚上回到家，虽然只有两个人，我们还是火火闹闹地做了一顿年夜饭，都是一些家常菜：
香肠和腊肉自然不会少；
豆瓣鲜鱼是下午现到中国店买的活鱼－吃它个年年有余（还故意剩下一些）；
泡椒墨鱼仔；
连锅汤煮青头萝卜；
红烧大肉丸子－团团圆圆过个年；
清炒青油菜－明年更年青；
年糕－年糕年糕，年年高升。

祝大家新年快乐！“猪”马精神！

今天花了3个小时跑到弗吉尼亚去买了几块巧克力。

那个地方叫Kingsbury Chocolates，某一天在报纸上看到。全手工做的新鲜巧克力，我觉得挺特别的。这两天天气太坏，下着大雪。还好不虚此行。小店在 Alexandria Old Town里，从地铁站出来，一路上都是各式各样的小店，看上去都挺有意思。我想如果周末天气好，这里说不定挺热闹。

这里买的各式巧克力做得都很漂亮，还没有尝味道，我就已经先入为主了。先选了一盒白巧克力。一共只有两种：Tiramisu和Cardamom Blueberry，所以一样要了三个。（插一句，方便之处是可以单个买，也可以买2个一盒，或者6个一盒，或者Ｎ个一盒的。种类可以自由搭配。）

Tiramisu – fresh honey & coffee ganache sprinkled with espresso.
Cardamom Blueberry – powdered cardamom whipped with blueberries soaked in crème de cassis.

后来又忍不住又买了三种。因为每种都没有试过，而且每种看上去都挺好的，所以真不好决定。好在店主挺有耐心。买了两块叫Rose Pedal的（如图），顶上顶了一片玫瑰花瓣，吃起来也有玫瑰的味道。在小店的网站上找不到这一种巧克力，看来是应景的（情人节）。最后看来看去，还是选了两种这里很出名的巧克力。一种叫Lavender Pistachio的。顶上有薰衣草的花瓣。咬一口满口都是花香。还有一种黑巧克力，叫Black Russian，味道很纯。

Lavender Pistachio – provence lavender & salt roasted pistachio's.
Black Russian – coffee liqueur & vodka ganache spinkled with espresso.

一个字：“千万不要浪费钱去看”! Period。

这年头，想花钱买几声廉价笑都不可得。

每次在ＯＵ图书馆的摄影图书区看到这张照片，我都想知道摄影师是谁。可惜一直到毕业离开ＯＵ都没有找到答案。今天在网上看一套有关布勒松(Henri Cartier-Bresson)的幻灯片（http://www.slate.com/id/2158859/fr/rss/）居然发现这张Martin Munkacsi的作品。正是这一张照片，让布勒松放弃了绘画，走上了摄影的道路。