The researchers built a mechanized rodent tanning salon and exposed mice engineered to lack the enzyme and normal mice to UV light three times a week for 20 weeks, enough to cause redness, but not to burn. At the end of the experiment, the engineered mice still had smooth, unblemished skin, while the normal mice were deeply wrinkled.
Granzyme B breaks down proteins and interferes with the organization and the integrity of collagen, dismantling the scaffolding — or extra-cellular matrix — that cells bind to. This causes structural weakness, leading to wrinkles. Sunlight appears to increase levels of the enzyme and accelerate its damaging effects.
Another reason for the sparse use of robots is that buildings require a lot more maintenance than just window cleaning. Equipment is needed to lower people to repair facades and broken windows, like the one that rescue workers had to cut through with diamond cutters to rescue the window washers. For many years, being a window cleaner in Manhattan was regarded as one of the most dangerous occupations in the world: by 1932, an average of one in every two hundred window cleaners in New York was killed each year. Now all new union window cleaners now take two hundred and sixteen hours of classroom instruction, three thousand hours of accredited time with an employer and their union makes sure workers follow rigorous safety protocols. In all, there are about 700 scaffolds for window washing on buildings in New York City, says union representative Gerard McEneaney. His members are willing to do the work because it pays well: as much $26.89 an hour plus benefits. Many of the window cleaners are immigrants from South America. "They're fearless guys, fearless workers."