Johnson Matthey is helping drag the chemicals sector lower. The platinum refiner and catalytic converter maker was downgraded to 'equal-weight' from 'overweight' at Morgan Stanley.Elsewhere in chemicals, Plant Health Care falls back slightly after depressed agricultural markets resulted in widening losses at natural plant supplement supplier.Drug giants AstraZeneca and GlaxoSmithKline are demonstrating their defensive qualities, rising amid a depressed market. Elsewhere in pharmaceuticals, Biotech ValiRx has created a new wholly owned trading subsidiary, ValiMedix, to distribute a range of new diagnostic screening products. Top performing sectors so far todayFood Producers & Processors 4,400.41 +0.80%Pharmaceuticals & Biotechnology 8,156.98 +0.68%Aerospace and Defence 2,846.64 +0.64%Mobile Telecommunications 3,162.83 +0.33%Bottom performing sectors so far todayAutomobiles & Parts 2,679.42 -3.62%Forestry & Paper 3,151.70 -2.86%Chemicals 4,043.99 -2.82%Industrial Metals 4,286.09 -2.48%Technology Hardware & Equipment 311.22 -2.03%