In this video lesson, Paul Gilbert explains how it can help your technique and writing to borrow licks from other instruments, particularly those quite far removed from the guitar, such as the piano.
Integral to this video lesson is the concept of outside picking. A lot of Paul's super-fast alternate picking is based around this principal, where he considers the most efficient pick movement from one string to another.
The first two notes, as Paul explains, are one semitone apart. This would typically be played on one string between your first and second fingers, but the challenge here is to play them across two strings. The first note should be played with an upstroke followed by a downstroke on the second note (ie, outside picking).
Take care not to let the two notes bleed into each other. Try muting the E string with the flat of your fourth finger when playing the D#. Avoid the strong temptation to move your hand excessively when moving between strings (especially away from the body of the guitar). It should move very little, in fact, so work on keeping the movement as efficient as possible.
It's then a case of co-ordinating your pick and fingers. Try this slowly at first, as you may trip over your fingers if you try it at Paul's speed. The second half of this lick features a string skip (again, reached with an outside pick). Notice how the slightly awkward technique of the first four notes makes moving to the string skip much easier than with a traditional method. It also helps achieve cleaner articulation. Any kind of single string semitone trill is difficult to play without legato phrasing (hammer-ons and pull-offs), so moving between strings can help create a stronger sound.
For more information on Paul, check out the official Paul Gilbert website.