Domain: Engineering — Agricultural Engineering
Target concept: Extracting soybean leaf protein and adding Coomassie Brilliant Blue, the solution turns from brown to purple within 3 seconds, while solutions without protein do not undergo color change.

Video generation prompt: Grind fresh soybean leaves and add buffer solution to extract soluble components. Filter the extract and divide it into two test tubes. Add Coomassie Brilliant Blue reagent to one tube and distilled water to the other. Gently mix and place the two tubes side by side for comparison. Only clear experimental equipment, reagents, and sequentially performed procedures are shown.

Evaluation guide:
(i) Target concept: Protein-dependent dye-binding colorimetric assay (Bradford-type).
Minimum mechanism: In the acidic Bradford reagent, free (unbound) Coomassie Brilliant Blue G-250 exists predominantly in its protonated, cationic form, which is reddish-brown (λmax ~465 nm). When soluble leaf protein is present, basic and aromatic amino acid residues on the protein bind the dye through ionic and hydrophobic interactions; this binding stabilizes the dye's unprotonated, anionic form, which is blue/purple (λmax ~595 nm), producing the visible brown-to-purple shift within seconds. This color shift requires soluble protein presence, adequate reagent concentration, and absence of interfering substances (e.g., detergents, reducing agents) that could disrupt dye-protein binding.
(ii)Storyline: Frame 1–2: Fresh green soybean leaves ground with colorless buffer → brown slurry forms. Frame 3–4: Brown extract filtered → clear brown filtrate collected. Frame 5–6: Filtrate divided equally into two identical upright test tubes. Frame 7: Reddish-brown Coomassie Brilliant Blue reagent dispensed into left tube; clear distilled water dispensed into right tube. Frame 8: Both tubes gently swirled simultaneously. Frame 9–10: Tubes held motionless, side-by-side, under uniform lighting: left tube fully purple, right tube fully brown. Perspective: Fixed frontal close-up, full-tube visibility, no occlusion, consistent focal plane across all frames.

Manual:
Experimental Procedure
1. Grind fresh soybean leaves with buffer solution in mortar.
2. Filter extract into a beaker.
3. Transfer equal volumes into two identical test tubes.
4. Add Coomassie Brilliant Blue reagent to first tube.
5. Add distilled water to second tube.
6. Gently mix both tubes.
7. Place tubes side by side for direct comparison.
Observation of Experimental Phenomena
The tube with Coomassie Brilliant Blue turns uniformly purple; the tube with distilled water remains brown. No color change occurs in the control tube.
Summary of Experimental Principles
Coomassie Brilliant Blue binds to proteins in the soybean leaf extract, forming a purple complex. Absence of protein prevents binding, so the control tube retains the original brown color of the extract.

Prompt Grounding rubric:
level_1: No visible grinding of soybean leaves; no buffer solution added; no filtration step shown; no test tubes present; no Coomassie Brilliant Blue reagent or distilled water visibly dispensed; no side-by-side tube placement; no mixing action shown.
level_2: At least one correct object present (e.g., test tubes or leaves), but critical steps missing: grinding absent, filtration absent, or reagents not dispensed into separate tubes; tubes not placed side-by-side; mixing not shown; sequence is disordered or unidentifiable.
level_3: All required objects present (soybean leaves, mortar/pestle, buffer solution, filter apparatus, two identical test tubes, Coomassie Brilliant Blue reagent bottle, distilled water bottle); grinding, filtration, tube filling, side-by-side placement, and gentle mixing are all shown; however, at least one object is mislabeled (e.g., the Coomassie reagent bottle labeled as water) or one action lacks clear causal linkage (e.g., reagent added before tube division).
level_4: All objects correctly identified and visually distinct (leaf material green and fibrous, buffer solution colorless and transparent, Coomassie Brilliant Blue reagent visibly reddish-brown/tan in its bottle, which is its natural color before contacting any protein, distilled water bottle clearly labeled or differentiated); all seven core steps shown in correct order: (1) grinding leaves, (2) adding buffer, (3) filtering extract, (4) dividing into two tubes, (5) adding Coomassie to first tube, (6) adding distilled water to second tube, (7) gentle mixing of both; tubes placed adjacent and stationary in same frame throughout comparison phase.
level_5: All objects present, correctly colored and labeled (Coomassie bottle a consistent reddish-brown/tan, water bottle clear/white-labeled, leaf material fresh-green with visible venation); every step occurs once, sequentially, without omission, duplication, or substitution (e.g., no pipette used for buffer if mortar is shown; no pre-filled tubes); both tubes remain identically oriented, fully visible, motionless during comparison; no extraneous tools, hands, or labels appear; camera viewpoint fixed, full-frame view of workspace with no cutaways or zooms disrupting continuity.

Scientific and Causal Correctness rubric:
level_1: No color change observed; both tubes remain same color (e.g., both brown, both purple, both colorless); or color change occurs in wrong tube (e.g., distilled water tube turns purple); or no tubes shown post-mixing.
level_2: Color change occurs, but in incorrect direction (e.g., purple → brown) or in both tubes; or only one tube shown after mixing; or color change appears instantaneous without mixing action preceding it; or initial extract is shown colorless instead of brown.
level_3: Extract appears brown before addition; Coomassie tube turns purple after mixing; distilled water tube remains brown; color difference between tubes is visible; however, either (a) the brown-to-purple transition is not temporally linked to mixing (e.g., color appears before mixing), or (b) distilled water tube shows slight tint (e.g., faint blue haze), or (c) extract is shown translucent instead of opaque-brown pre-addition.
level_4: Pre-mixing: extract in both tubes is uniformly brown and opaque; post-mixing: Coomassie tube is uniformly purple and opaque; distilled water tube remains uniformly brown and opaque; no hue bleed, gradient, or transparency difference between tubes; color states are stable during side-by-side comparison; no flicker, fade, or desaturation during transition.
level_5: Pre-mixing state: extract is identifiably brown (not yellow, red, or gray) and fully homogeneous in both tubes; immediately after mixing, Coomassie tube exhibits abrupt, complete, uniform purple coloration with no residual brown patches or streaks; distilled water tube retains identical brown appearance with zero chromatic shift; purple and brown hues are spectrally distinct and non-overlapping under consistent lighting; color states persist unchanged for entire comparison duration.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal violations: the mortar, filter funnel, or either test tube snaps to a different bench position or vanishes/reappears between the grinding, filtration, dividing, or comparison frames; the two tubes swap left/right positions between the mixing step and the final side-by-side comparison; the bench lighting flips abruptly (e.g., bright to dark) between the grinding shot and the comparison shot; the brown-to-purple change happens across a hard cut with the tubes in visibly different positions immediately before and after.
level_2: Moderate violations: the left/right arrangement of the Coomassie tube and the water tube is inconsistent between the swirling step and the comparison step; the swirling hand motion jumps or cuts rather than following a continuous path from grasp to swirl to set-down; the filtrate level visibly differs between the two tubes even though both were poured from the same filtrate volume; the bench lighting's brightness or color temperature noticeably shifts between the filtration shot and the comparison shot; the mortar or filter funnel appears or disappears between frames without ever being moved off-screen.
level_3: Minor but detectable violations: a brief, visible jitter in tube alignment while the two tubes sit side by side; a hand or dropper lingers over a tube long enough to briefly hide its liquid level during the moment the dye or water is added; the mortar's shadow on the bench appears to shift direction once during grinding even though nothing indicates the light source moved; the swirling motion shows a brief speed hiccup but still completes in one continuous direction to the same end position.
level_4: Across grinding, filtration, dividing, and comparison, the mortar, filter funnel, and both test tubes keep consistent relative bench positions except when a hand is actively moving them; no hand, cap, or dropper blocks the view of either tube's liquid level or color during the pouring or dye-adding moments; the swirling and pouring motions trace continuous, physically plausible paths (e.g., the dropper tip visibly enters the tube mouth before liquid appears, rather than the liquid appearing first); the mortar's shadow during grinding and the two tubes' shadows during the side-by-side comparison each keep a consistent direction and length within their own segment; no flicker, warping, or stretching affects the tubes, funnel, or bench surface at any point.
level_5: From the first grinding frame through the final side-by-side hold, the mortar, filter funnel, and both test tubes show no drift, snapping, or duplication in their bench positions; the liquid surface in each tube changes smoothly with no sudden jump in level or meniscus shape between adjacent frames; the shadow cast by the mortar during grinding and the shadow cast by the two tubes during the final comparison each hold a steady direction and softness throughout their own segment, with no visible brightness pulsing or color flicker on the tubes or bench between neighboring frames; the whole sequence reads as one continuous, uncut take, with no visible splice, dissolve, or stabilization warp at any transition.