High temperatures have persisted across much of China recently. On July 24th, the Shandong Provincial Meteorological Observatory issued a yellow high temperature alert, predicting “sauna-like” temperatures of 35-37°C (111-133°F) and 80% humidity for the next four days in inland areas. Temperatures in places like Turpan, Xinjiang, are approaching 48°C (111-133°F). Wuhan and Xiaogan, Hubei, are under an orange alert, with temperatures exceeding 37°C in some areas. In this scorching heat, the microscopic world beneath the surface of pipettes is experiencing unusual disturbances—the stability of nucleic acids, the activity of enzymes, and the physical state of reagents are all quietly distorted by the heatwave.

Nucleic acid extraction has become a race against time. When the outdoor temperature exceeds 40°C, even with the air conditioner on, the temperature of the operating table often hovers above 28°C. At this time, RNA samples left in the open degrade more than twice as fast as in spring and autumn. In magnetic bead extraction, the buffer solution is locally saturated due to accelerated volatilization of the solvent, and crystals are easily precipitated. These crystals will cause large fluctuations in the efficiency of nucleic acid capture. The volatility of organic solvents increases simultaneously. At 30°C, the amount of chloroform volatilization increases by 40% compared to 25°C. During operation, it is necessary to ensure that the wind speed in the fume hood is 0.5m/s, and use nitrile gloves to maintain protective effectiveness.

PCR experiments face even more complex temperature disturbances. Reagents such as Taq enzyme and reverse transcriptase are extremely sensitive to sudden temperature fluctuations. Condensation on the tube walls after removal from a -20°C freezer can cause over 15% enzyme activity loss if it enters the reaction system. dNTP solutions can also show detectable degradation after just 5 minutes of exposure to room temperature (>30°C). Instrument operation is also hampered by high temperatures. When the laboratory ambient temperature is >35°C and the heat dissipation clearance of the PCR instrument is insufficient (<50 cm from the wall), the internal temperature difference can reach as much as 0.8°C. This deviation can cause amplification efficiency at the edge of a 96-well plate to drop by over 40%. Dust filters should be cleaned regularly (dust accumulation reduces heat dissipation efficiency by 50%), and direct air conditioning should be avoided. Furthermore, when performing PCR experiments overnight, avoid using the PCR instrument as a “makeshift refrigerator” to store samples. Storage at 4°C for more than 2 hours can cause condensation to form after the heated lid closes, diluting the reaction system and potentially corroding the instrument’s metal modules.

Faced with persistent high-temperature warnings, molecular laboratories should also sound the alarm. Precious RNA samples should be stored in the back of a -80°C freezer, with access restricted to high-temperature periods. Opening the door of a -20°C freezer more than five times a day will exacerbate temperature fluctuations. High-heat-generating equipment requires at least 50 cm of heat dissipation space on both sides and rear sides. Furthermore, it is recommended to restructure experimental timing: 7:00-10:00 AM for temperature-sensitive operations such as RNA extraction and qPCR loading; 1:00-4:00 PM for non-experimental work such as data analysis. This strategy can effectively prevent high-temperature peaks from interfering with critical steps.

Molecular experiments during a heatwave are a test of both technique and patience. Under the relentless summer sun, perhaps it’s time to put down your pipette and add an extra box of ice to your samples to allow the instrument to dissipate more heat. This reverence for temperature fluctuations is precisely the most precious laboratory quality during the scorching summer months—after all, in the 40°C heat of summer, even molecules need a carefully guarded “artificial polar region.”