每日英語跟讀 Ep.846: Why Soap Works 為何肥皂能對付細菌和病毒？

It probably began with an accident thousands of years ago. According to one legend, rain washed the fat and ash from frequent animal sacrifices into a nearby river, where they formed a lather with a remarkable ability to clean skin and clothes. Perhaps the inspiration had a vegetal origin in the frothy solutions produced by boiling or mashing certain plants. However it happened, the ancient discovery of soap altered human history. Although our ancestors could not have foreseen it, soap would ultimately become one of our most effective defenses against invisible pathogens.

肥皂很可能源自幾千年前的一次意外發現。有個傳說這麼說，雨水把經常以動物獻祭留下的脂肪和灰燼沖到附近一條河中，形成了清潔皮膚和衣物效力驚人的泡沫。也許發明肥皂的靈感來自植物，來自把某些植物煮沸或搗碎成泥後產生的泡沫溶劑。不論肥皂如何發明，這個古老發現改變了人類史。雖然我們的祖先無法預見，肥皂最終卻成了我們防禦不可見的病原體的一大利器。

People typically think of soap as gentle and soothing, but from the perspective of microorganisms, it is often extremely destructive. A drop of ordinary soap diluted in water is sufficient to rupture and kill many types of bacteria and viruses, including the new coronavirus that is currently circling the globe. The secret to soap’s impressive might is its hybrid structure.

人們通常認為肥皂溫和怡人，但從微生物的角度來看，肥皂往往極具摧毀力。一滴普通肥皂的肥皂水足以破壞並殺死多種細菌和病毒，包括目前全球散播的新冠病毒。肥皂威力驚人，祕密在於其混合結構。

Soap is made of pin-shaped molecules, each of which has a hydrophilic head — it readily bonds with water — and a hydrophobic tail, which shuns water and prefers to link up with oils and fats. These molecules, when suspended in water, alternately float about as solitary units, interact with other molecules in the solution and assemble themselves into little bubbles called micelles, with heads pointing outward and tails tucked inside.

肥皂由大頭針形狀的分子構成，每個分子都有親水性的頭，容易跟水結合，還有疏水性的尾巴，避開水而傾向與油脂結合。這些分子懸浮在水中時，輪流以單個單元的形態漂浮，與溶劑中其他分子互動，並與其他分子結合成為小氣泡，稱為「微胞」，頭朝外，尾巴向內收攏。

Some bacteria and viruses have lipid membranes that resemble double-layered micelles with two bands of hydrophobic tails sandwiched between two rings of hydrophilic heads. These membranes are studded with important proteins that allow viruses to infect cells and perform vital tasks that keep bacteria alive. Pathogens wrapped in lipid membranes include coronaviruses, HIV, the viruses that cause hepatitis B and C, herpes, Ebola, Zika, dengue, and numerous bacteria that attack the intestines and respiratory tract.

一些細菌和病毒有脂質膜，這種膜像是雙層微胞，兩圈疏水性的尾巴被兩圈親水性的頭包夾。這些膜密布著重要的蛋白質，蛋白質使病毒有能力感染細胞，並負責維持細菌存活的重要任務。有脂質膜的病原體包括冠狀病毒、人類免疫缺乏病毒、導致B型和C型肝炎的病毒、疱疹、伊波拉、茲卡、登革病毒，以及眾多攻擊腸道和呼吸道的細菌。

When you wash your hands with soap and water, you surround any microorganisms on your skin with soap molecules. The hydrophobic tails of the free-floating soap molecules attempt to evade water; in the process, they wedge themselves into the lipid envelopes of certain microbes and viruses, prying them apart.

當你用肥皂和水洗手時，你是用肥皂分子包圍皮膚上的所有微生物。自由漂動的肥皂分子的疏水性尾巴努力避開水，在這過程中，這些尾巴插入一些細菌和病毒的脂質外層，把外層撬開。

“They act like crowbars and destabilize the whole system,” said professor Pall Thordarson, acting head of chemistry at the University of New South Wales. Essential proteins spill from the ruptured membranes into the surrounding water, killing the bacteria and rendering the viruses useless.

澳洲新南威爾斯大學化學系代理主任索達森教授說：「這些尾巴的作用就像鐵撬，破壞整個系統。」重要蛋白質從破掉的膜散落到周圍的水中，使細菌死亡，病毒失效。

In tandem, some soap molecules disrupt the chemical bonds that allow bacteria, viruses and grime to stick to surfaces, lifting them off the skin. Micelles can also form around particles of dirt and fragments of viruses and bacteria, suspending them in floating cages. When you rinse your hands, all the microorganisms that have been damaged, trapped and killed by soap molecules are washed away.

一些肥皂分子會聯手破壞使細菌、病毒和汙垢附著在皮膚表面上的化學鍵，把這些汙物帶離皮膚。肥皂微胞也能在汙垢粒子和病毒細菌碎片周圍形成，把汙物關在漂浮的牢籠中。當你洗手時，所有被肥皂分子破壞、困住和殺死的微生物都被沖走。

Source article: https://paper.udn.com/udnpaper/POH0067/351877/web/